Computer Science · Grade 10

Active learning ideas

Defining and Calling Functions

Teaching functions through active learning turns abstract concepts into concrete experiences. Students see firsthand how reusing code saves effort and reduces errors, which builds confidence and long-term retention. Hands-on practice also lets them test their own assumptions, turning confusion into clarity through immediate feedback.

• Ontario Curriculum Expectations
• CS.HS.P.3
• CS.HS.P.4

• 25–45 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Peer Teaching
• 35 min · Pairs

Pair Programming: Shape Calculator Functions

Pairs write three functions: one for circle area, one for rectangle area, and one to compare results. They call each with user inputs and refactor a script with repeated calculations. Pairs swap code to test and suggest improvements.

Analyze how functions reduce code redundancy and improve modularity.

Facilitation Tip

During Pair Programming, circulate and ask each pair to explain why they chose a particular parameter name, reinforcing the connection between function design and real-world use.

What to look for

Provide students with a short Python code snippet containing repeated lines of code. Ask them to write a function that encapsulates the repeated logic and then rewrite the snippet using their new function. They should also identify one variable that would have local scope within their function.

• Understand
• Apply
• Analyze
• Create
• Self-Management
• Relationship Skills

Activity 02

• Peer Teaching
• 40 min · Small Groups

Small Groups: Scope Debugging Challenge

Groups receive buggy code with scope errors, like modifying global variables inside functions. They predict outcomes, run the code, trace variable changes, and rewrite with proper local variables. Discuss fixes as a group before sharing one solution with the class.

Construct a function to perform a specific task with given inputs.

Facilitation Tip

In the Scope Debugging Challenge, provide code with intentional scope errors and ask groups to trace variable lifetimes using highlighters or annotations on printed listings.

What to look for

Present students with a simple function definition and several function calls with different arguments. Ask them to predict the output for each call and explain why. For example: 'def greet(name): print(f'Hello, {name}!')'. Then ask: 'What will be printed if we call greet('Alice')? What about greet('Bob')?'

• Understand
• Apply
• Analyze
• Create
• Self-Management
• Relationship Skills

Activity 03

• Peer Teaching
• 45 min · Whole Class

Whole Class: Function Design Relay

Divide class into teams. Each team starts a function for a task like string manipulation, passes it to the next team to add parameters and calls, then iterates until complete. Class votes on the most modular final function.

Explain the concept of scope for variables defined within and outside functions.

Facilitation Tip

For the Function Design Relay, prepare a set of starter function signatures on cards so students can physically arrange and test their sequence of calls.

What to look for

Ask students: 'Imagine you are building a calculator program. What are some tasks that could be efficiently handled by creating separate functions? For each function you identify, what inputs (parameters) would it need, and what output (return value) would it produce?'

• Understand
• Apply
• Analyze
• Create
• Self-Management
• Relationship Skills

Activity 04

• Peer Teaching
• 25 min · Individual

Individual: Personal Code Refactor

Students select their own prior program with redundancy, identify repeatable logic, define functions to replace it, and document before-and-after differences. They run tests to verify functionality and submit reflections on improvements.

Analyze how functions reduce code redundancy and improve modularity.

Facilitation Tip

In Personal Code Refactor, remind students to leave comments in their original messy code so they can compare it to their clean version during reflection.

What to look for

Provide students with a short Python code snippet containing repeated lines of code. Ask them to write a function that encapsulates the repeated logic and then rewrite the snippet using their new function. They should also identify one variable that would have local scope within their function.

• Understand
• Apply
• Analyze
• Create
• Self-Management
• Relationship Skills

A few notes on teaching this unit

Teachers find success when they treat functions as tools, not just syntax. Begin with physical metaphors, like passing labeled objects to a teammate who performs a task and returns a result. Avoid overloading students with too many rules at once. Instead, let them discover patterns through repeated use, and correct misconceptions as they arise during active work.

By the end of these activities, students will define functions with parameters, call them with arguments, and track variable scope. They will explain why functions improve program structure and identify when to use returns versus prints. Successful learning shows in clean, reusable code and clear explanations of execution flow.

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Watch Out for These Misconceptions

• During Pair Programming: Shape Calculator Functions, watch for students who define functions but forget to call them or assume functions run automatically.

  Remind pairs to swap laptops and run each other’s code, inserting print statements right after function calls to visibly confirm execution and reinforce the need for explicit calls.

• During Scope Debugging Challenge, watch for assumptions that variables inside functions remain available outside their blocks.

  Have groups annotate each variable with its lifetime using color codes, then test predictions by running the code in a debugger and observing when variables disappear from the local scope.

• During Function Design Relay, watch for students who treat return values as optional or print them instead of using them in further calculations.

  Provide a worksheet where students must assign return values to variables before using them in the next function call, making the flow of data explicit and correcting the misconception through immediate testing.

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Methods used in this brief

• Peer Teaching