How To Teach Computer Science In High School

Transcription

1 Methods of Teaching a Computer Science Course for Prospective Teachers Tami Lapidot and Orit Hazzan Department of Education in Technology and Science Technion Israel Institute of Technology Haifa, Israel {lapidot, oritha}@tx.technion.ac.il Abstract This article focuses on a Methods of Teaching Computer Science in the High School course (abbreviated MTCS). It presents the rationale and need for the course, and suggests optional course frameworks and implementations that are not limited to a particular programming language, programming paradigm, level of students, or curriculum. 1. Introduction The Report of the ACM K-12 Education Task Force [Tucker et al., 2002] draws attention to the need for appropriate teacher training programs and points out that teachers must acquire both a mastery of the subject matter and the pedagogical skills that will allow them to present the material to students at appropriate levels. Our literature review hints that this call, for the establishment of teacher preparation programs, is still waiting for an answer. Specifically, as it turns out, it is difficult to find in the computer science education literature a discussion about a Methods of Teaching Computer Science in the High School course (henceforth abbreviated as MTCS), that both concentrates solely on computer science ideas and supports the K-12 computer science curriculum currently undergoing development. This article attempts to respond to this call. Specifically, it presents the rationale for an MTCS course, suggests possible frameworks for such a course, and illustrates methods for implementation. The discipline of computer science is appearing in the high school curriculum both in the US and in other countries [cf. Gal-Ezer et al., 1995; Tucker et al., 2002]. These new curricula raise several questions from a teaching perspective. How should computer science teachers be properly educated? Should their training be different from that of teachers in other fields of science? What appropriate framework would fit for an MTCS course? Which topics should be included in such a course? Which kind of activities will be best suited for the preparation of future computer science teachers? What types of assessment and evaluation are appropriate for the prospective teachers participating in the MTCS course? These issues deserve an examination when the computer science community develops teacher preparation programs. An examination of the methods courses offered by educational departments reveals that in most cases separate methods courses are offered for teaching mathematics and science, alongside methods courses for teaching other disciplines such as English(1). With respect to each discipline, most institutions offer two courses, one dedicated to the teaching of the discipline in the elementary school and a second dedicated to its teaching in the high school. As it turns out, MTCS courses frequently address topics related mainly to programming, computer literacy, and the integration of computers in the secondary school(2) in general(3). In other cases, methods of teaching computer science in the secondary school are discussed as part of the Methods of Teaching Sciences in the Secondary School course. Based on our literature review, web search, and personal conversations with high school computer science educators, it seems that comprehensive MTCS courses for the high school level are rarely available. The planning of an MTCS course can be facilitated by an examination of existing courses in other areas. Thus, in what follows we briefly present examples of rationales of methods courses for teaching science and mathematics in the secondary school. Courses on teaching secondary school science usually emphasize several aspects. For example, in the Science Methods course offered at Georgia Southern University the emphasis is placed on planning and presentation of skills and on developing strategies to facilitate working with the diverse student populations present in public schools (4). The Methods of Teaching Secondary Science course offered at the University of New Hampshire emphasizes the [a]pplication of theory and research findings in science education to classroom teaching with inroads The SIGCSE Bulletin 29 Volume 35, Number 4, 2003 December

2 emphasis on inquiry learning, developmental levels of children, societal issues, integration of technology, critical evaluation of texts and materials for science teaching, and planning for instruction. (5) In general, courses on teaching secondary school science emphasize curriculum issues, address topics such as learning theory and instructional strategies in science, principles of the development and selection of science curricula, special aspects of laboratory instruction and other investigative methods, professional ethics in science instruction, and the place of science in education. In the case of mathematics, we find many methods courses. Most of them discuss modes of instruction, problem solving, use of technology, assessment, and national standards. In the 2002 fall semester, the University of Arizona in Tucson offered an example of such a course(6). Among other objectives and goals, it mentions the following issues in the course description: Students will be able to develop lessons and lesson plans for the different modes of instruction; Students will appreciate the importance of problem solving in the mathematics curriculum, and will be able to integrate it into all content area topics; Students will know and be able to develop a variety of means of evaluating student learning. 2. Frameworks for the MTCS Course We believe that a comprehensive MTCS course should address similar variety of viewpoints as presented in the above examples. Indeed, educational research studies and articles from the last fifteen years indicate that professional teachers require a wide variety of knowledge areas and expertise. According to NCATE (National Council for Accreditation of Teacher Education) standards (presented in [Tucker et al., 2002]), in addition to their knowledge of the subject matter, as is reflected in the case of computer science in the undergraduate programs in computing (Computing Curricula 2001), teachers should also be qualified to design lessons and learning activities. They should also plan and deliver units of instruction, develop assessment strategies, develop a personal plan for evaluating their own practice of teaching, and other capabilities that require diverse types of knowledge. Consequently, the education and training of prospective teachers of any subject should address this diversity. However, one can use different approaches for the organization of such a course. We suggest four frameworks for the MTCS course: the NCATE standards, merger of computer science with pedagogy, Shulman s model of teachers knowledge, and research findings. The first proposed framework for the MTCS course is based on the NCATE standards [Tucker et al., 2002]. Among the 13 standards, teachers are expected to learn how to plan lessons/modules related to programming process and concepts, and issue examination (Standard 2). They also should be able to develop assessment strategies appropriate to lesson goals (Standard 3), and address student population characteristics (Standard 4). Section 3 of this article offers a possible implementation of the theme of evaluation as is derived from NCATE standards. The second optional framework is based on the special amalgam of the two disciplines: computer science and pedagogy. Although pedagogical principles and teaching methods are learnt in other general pedagogical courses of teacher preparation programs, we believe that an MTCS course should focus on their implications and adoption into the context of computer science education. Accordingly, if chosen as a framework for the MTCS course, the organizing idea is a merger of computer science with pedagogy into one amalgam of content and pedagogy. From a pedagogical point of view, this framework addresses topics such as the introduction and summary of a specific topic, learning in groups, learning by inquiry, and planning constructivist activities. It also addresses the creative and non-conventional use of the computer laboratory, the analysis of teaching difficulties and possible obstacles, the adjustment of learning materials for students with different needs, definitions and their role in learning processes, and the use of metaphors, multimedia and games in computer science education. Section 4 offers one possible implementation as derived from this amalgam for the computer science theme of soft ideas. The third optional framework for the MTCS course is based on Shulma s model of the teaching knowledge base [Shulman, 1987], which consists of seven categories: content knowledge, general pedagogical knowledge, curriculum knowledge, pedagogical content knowledge, knowledge of learners and their characteristics, knowledge of educational context, and knowledge of educational ends. We believe that all these categories should be included in the MTCS course. However, as Shulman recommends that [a]n emphasis on pedagogical content knowledge [should] permeate the teacher preparation curriculum [1987, p. 20], we believe that the pedagogical content knowledge (PCK) category is the most important one. Due to space limitations, we just mention a few core concepts that may be included in the MTCS course with respect to their PCK: programming and algorithm design, data representation and information organization, debugging, and abstraction. Teachers should address each of such topics in the course, with full attention to different aspects such as best representations of ideas, analogies, illustrations, examples, explanations, and learners difficulties. The fourth optional framework is based on research findings. The extensive research in computer science education conducted in the last years may provide such a framework by focusing on known misconceptions or difficulties. Variables, for example, are an excellent example for such a topic. Variables play an essential role in most programming languages and, as indicated by research in the field of computer science education, learners often face difficulties in understanding the various inroads The SIGCSE Bulletin 30 Volume 35, Number 4, 2003 December

3 aspects of the subject (Pea, 1986; Spohrer & Soloway, 1986; and Samurçay, 1989 are just a few examples). In the next two sections, we suggest two optional implementations of the MTCS course frameworks. We present each implementation as a cluster of optional activities. The order in which we present the activities is optional. In practice, one can arrange activities into the MTCS course to meet the needs of the prospective teachers and the local computer science curriculum. 3. The Theme of Evaluation Evaluation is one of the traditional tasks teachers have to master from the very beginning of their professional lives. The follows three activities demonstrate how one can address the theme of evaluation in the MTCS course. Specifically, the presented activities focus on tests, and address the preparation of tests and their grading. Activity 1 This activity consists of a class discussion about topics addressed by a teacher when composing a test. The teacher should raise the following topics in such a discussion: the target and structure of the test, different ability levels of students, types of questions, different complexity levels of questions, matching questions to the class level, organization of the questions in the test, and grading policies. This discussion aims to increase the prospective teachers awareness to the fact that the construction of a test is not a trivial task and that great attention must be devoted to a variety of issues. Activity 2 In this activity, students work in teams to construct questions of different levels and types (i.e. simple and complex questions). This activity is conducted after students are presented with a list of different kinds of questions, such as closed questions (e.g., Select the correct answer ), programming questions (e.g., Write a computer program that ), and comparison questions (e.g., Which of two given computer programs performs a given task more efficiently ). By constructing questions of different levels, the prospective teachers are encouraged to analyze topics and questions such as, what factors influence the level of a particular question, different approaches learners may adopt when solving a given question, learners mental processes, and the matching of questions to a specific group of learners. Following this activity, the teacher may ask students to construct an entire test on a specific topic. Activity 3 In this activity, students evaluate a genuine answer that was given by a high school pupil in a genuine exam. The idea behind this activity is to address both computer science topics, such as the structure of a computer program or the role of arrays, and pedagogical ideas, such as how to evaluate a given answer. Other relevant issues addressed in this activity include questions such as: How are the pupil s intentions inferred from his or her written answer? Should teachers award points for the correct parts of the pupil s answer? Alternatively, when a mistake is observed, should teachers subtract points from the total points allocated to a specific question? What is the weight of each mistake? Should we distinguish between logical mistakes, syntax mistakes, programming style issues? Technically, we conduct this activity as follows: Students are presented with a question from an actual test, alongside a pupil's authentic answer to that question (see Appendix). Working in teams, teachers ask students to read the answer, try to understand the pupil's intentions, and explain why the pupil answered as he or she did. Then, they are asked to mark all the mistakes in the answer. In the next step, the students take a clean copy of the answer and write what they would communicate to the pupil if that paper were the pupil's exam notebook. Finally, the prospective teachers are asked to discuss and decide how they would grade this answer. Each of these activities is a subject for a class discussion. Some of the important conclusions that emerge from these activities are that there is no single and unique way to evaluate an exam and that different approaches may be applied in the process of exam evaluation. These approaches, however, should make sense, and when appropriate, should be explained to the pupils taking the exam. In addition, these activities increase the prospective teachers awareness that they can convey different messages (sometimes hidden) to pupils through teachers comments on pupils exam papers. 4. The Theme of Soft Ideas The merging of computer science with pedagogy offers many interesting topics for the MTCS course. Among these issues is the teaching of soft ideas (such as software development methods) versus teaching of concepts (such as variables or loops) or other hard ideas. The discussion in this section focuses on computer science heuristics such as abstraction, top-down development, and successive refinement. An examination of these ideas in the computer science literature reveals that these concepts are not simple. [For example, Liskov and Guttag (1986)] describe abstraction as a way to do decomposition productively by changing the level of details to be considered. We can view the process of abstraction as an application of manyto-one mapping. It allows us to forget information and consequently to treat things that are different as if they were the same. We do this in the hope of simplifying our analysis by separating attributes that are relevant from those that are not.[p. 3]. In what follows, we demonstrate the merger of computer science with pedagogy framework by five activities that deal with the concept of abstraction. A similar discussion, however, can be conducted with respect inroads The SIGCSE Bulletin 31 Volume 35, Number 4, 2003 December

4 to other methodologies and topics, such as operating systems or data abstraction. In addition, although the activities focus on abstraction, it is important to note that ideas such as abstraction should not be addressed as isolated topics. Rather, they should be addressed, referred to, and highlighted at any appropriate opportunity. Still, since such topics are complex in nature and are usually addressed in relation to other (sometimes-complex) topics, the special attention they receive in the MTCS course can highlight their importance in the eyes of the prospective teachers. Activity 1 Based on their familiarity with the concept of abstraction from their computer science courses, students are asked to define the term abstraction. After the definitions are collected and discussed, a short lecture is given that summarizes the students contributions and adds concluding remarks from the computer science literature. This activity can serve as a good opportunity to discuss with the prospective teachers the role of definitions in learning processes in general. For example, one teaching dilemma in this context would be the best timing to introduce a full and formal definition. Activity 2 Students are asked to design activities for the teaching of abstraction. The working assumption behind this task is that when one teaches a certain concept, especially a complex concept such as a development heuristics for computer programs, one deepens one s own understanding of that concept. After working in teams on this task, the students present the activities to their classmates. Indeed, as is intended, when students present the activities they have designed, many issues related to the concept of abstraction are clarified, elaborated on, and refined although it was not pre-declared as part of their task. Since the planning of learning activities is not a trivial task and different planning considerations for different topics exist, the planning of learning activities should be repeated in the MTCS course with respect to different topics. For example, if students design activities for the teaching of abstraction, it does not imply automatically that the same considerations should be taken when activities for the learning of sorting algorithm are designed. Activity 3 Students are requested to explain why methodologies such as abstraction are difficult to teach. In order to illustrate the pedagogical potential of this activity, we present some of the explanations presented by prospective teachers: In order to teach abstraction we need concrete examples, and thus we lose the generality inherent in the topic. Effective discussion and demonstration of the power of abstraction [ ] can be carried out only when based on complex problems. These complex problems may distract our attention from the topic and we should share our mental resources between the problem itself and thinking about the methodology (such as abstraction). There is a gap between programming, which is a real action, and learning problem solving methodologies, which is about thinking. Since abstraction [ ] [is] an individual process, there is no unique way to do it, so how can one teach these heuristics? These utterances reveal that by asking the prospective teachers to analyze the teaching of a particular topic, they are indirectly induced to examine the concept itself and analyze its properties. In the above quotes, we can see how the prospective teachers refer to topics such as relationships between thinking-with-examples and abstract thinking, limitations of the human mind, thinking processes, and the fact that there is no unique way to implement ideas such as abstraction. It seems reasonably that such analysis improve the prospective teachers' understanding of the topic discussed. Activity 4 This activity consists of a class discussion on the question: Is it possible to teach programming heuristics in the same way in which other computer science ideas are taught? This discussion addresses the multi-facet nature of topics such as abstraction, and serves as an excellent opportunity to discuss the teaching of other soft ideas versus the teaching of hard ideas in computer science. We also recommend to prepare with the students a list of concepts and ideas taken from the discipline of computer science and to ask to sort these concepts into sets of soft and hard topics. This activity leads naturally to interesting discussions such as, is recursion a soft or hard topic? Activity 5 In another context, the teaching of software methodologies such as abstraction can be addressed as part of a discussion held with prospective teachers about the guiding of high school pupils in the development of software projects. 5. Summary This article presents our first attempt to address Tucker et al. s call that refers to the need for appropriate teacher training programs [Tucker et al., 2002]. The suggestions presented in this article are based on our personal experience of teaching an MTCS course in the past decade. Specifically, we explain the rationale for the MTCS course and present optional course frameworks and implementations. It is important to note that the suggested frameworks and implementations are not limited to a particular programming language, programming paradigm, level of students, or curriculum. The examination of the MTCS course from the framework perspective is only one way to discuss the course. Indeed, the course can be highlighted from additional viewpoints, such as the teaching methods inroads The SIGCSE Bulletin 32 Volume 35, Number 4, 2003 December

5 employed in the course, the evaluation of the prospective computer science teachers participating in the MTCS course, and the prospective teachers teaching-practice in the high school. In future work we intend to address these viewpoints. Acknowledgments We would like to thank Professor Uri Leron, Drs. Dalit Levy, and Tamar Paz for their helpful comments on an earlier draft of this article, as well as for their cooperation and contribution to the development of the MTCS course. We would also like to thank our students in the last decade that completed the MTCS courses taught at the Department of Education in Technology and Science of the Technion Israel Institute of Technology. References [1] Computing Curricula 2001, The Joint Task Force on Computing Curricula IEEE Computer Society and the Association for Computing Machinery. [2] Gal-Ezer, J., Beeri, C., Harel, D., Yehudai, A. (October 1995). A high school program in Computer Science, Computer, [3] Liskov, B. and Guttag, J. (1986). Abstraction and Specification in Program Development. The MIT Press. [4] Pea, R. D. (1986). Language-independent conceptual bugs in novice programming, Journal of Educational Computing Research 2(1), [5] Shulman, L. S. (1987). Knowledge and teaching: Foundations of the new reform, Harvard Educational Review 57(1), [6] Spohrer, J.G. and Soloway, E. (1986). Analyzing the high frequency bugs. In E. Soloway and Y. Iyengar (eds.). Empirical Studies of Programmers, Albex Publishing Corporation, Norwood, New Jersey, [7] Samurçay, R. (1989). The concept of variable in programming: its meaning and use in problem-solving by novice programmers. In E. Soloway and J. C. Spohrer (eds.). Studying the Novice Programmer, Lawrence Erlbaum Associates, Publishers, New Jersey, [8] Tucker, A., Deek, F., Jones, J., McCowan, D., Stephenson, C. and Verno, A. (2002). A Model Curriculum for K-12 Computer Science: Report of the ACM K-12 Education Task Force Computer Science Curriculum Committee Draft. Endnotes (1) This conclusion is based mainly on an intensive web search. (2) In this article, the term "secondary school" refers to middle school and high school, whereas "high school" refers only to the higher grades and does not include the middle school grades (junior high). (3) For example, the course that was offered by the University of Saskatchewan [p]repares majors and minors to teach Computer Science in the secondary schools of the province. [ ] The development of problem solving skills needed for success in computer programming will be included. The URL of this course is (4) (5) (6) Appendix Test Evaluation Activity Worksheet MTCS Course - Class Activity The following question was presented to a class of high school pupils on a test: Write a Pascal program that receives, as input, a natural (positive integer) number N proceeded by N grades (each of them in the range of 0-100). The program should calculate and print: 1. The average of all grades. 2. The number of grades that are higher than The lowest grade. 4. The number of grades that are higher than the average (found in #1). Instructions: Following is a pupil's genuine answer. inroads The SIGCSE Bulletin 33 Volume 35, Number 4, 2003 December

6 Read the answer, try to understand the pupil's intentions and explain why the pupil wrote what he or she did. Mark all mistakes and problems you can find in the answer. Take a clean copy of the answer and regard it as if it was the pupil's exam paper. Determine what to write to the pupil and how to present him or her with your comments. Discuss and decide what grade (out of 30) should be given for this answer. PROGRAM MT; VAR W, Z, X, A, N, F : INTEGER; BEGIN W := 0; Z := ,2,3 FOR I := 1 TO N number of grades BEGIN READ (A); the grades X := X+A; the sum END; 1) MEMO := (X/N); average IF A > 55 THEN W := W+1 IF A < Z THEN Z := A IF A > MEMO THEN F := F+1 END; WRITELN MEMO; W; Z; F END. Bridge the Past with the Present through the IEEE Annals of the History of Computing Feature Articles Events and Sightings Reviews Biographies Anecdotes Calculators Think Piece Subscribe today! < inroads The SIGCSE Bulletin 34 Volume 35, Number 4, 2003 December