Computing · Year 6

Active learning ideas

Debugging Strategies for Logic Errors

Active learning works because debugging logic errors requires students to slow down and observe code behavior, not just read it. By physically tracing steps, swapping roles, and testing edge cases, students build the habit of methodical reasoning that turns vague hunches into precise fixes.

• National Curriculum Attainment Targets
• KS2: Computing - Programming and Algorithms
• KS2: Computing - Computational Thinking

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

Activity 01

• Jigsaw
• 35 min · Pairs

Pair Swap: Logic Bug Hunt

Each student creates a short program with a conditional statement, such as scoring in a game. Partners swap code, introduce one deliberate logic error, then debug it using print statements and edge-case tests. Pairs discuss fixes and swap back to verify.

Explain a systematic approach to finding a logic error in a conditional statement.

Facilitation Tip

During Pair Swap: Logic Bug Hunt, circulate and listen for students verbalizing their hypothesis before changing code, reinforcing that debugging is thinking, not clicking.

What to look for

Provide students with a short program containing a clear logic error in an 'if' statement (e.g., checking if a score is greater than 100 when it should be greater than or equal to 100). Ask them to identify the incorrect condition and rewrite it correctly.

• Understand
• Analyze
• Evaluate
• Relationship Skills
• Self-Management

Activity 02

• Jigsaw
• 45 min · Small Groups

Small Groups: Trace Table Challenge

Provide groups with printed buggy code snippets involving if-else logic. Students fill trace tables to predict outputs, run the code, and identify discrepancies. Groups present one fix with evidence from their tables.

Compare different debugging tools or techniques for identifying incorrect conditions.

Facilitation Tip

During Trace Table Challenge, project one example row at a time so the whole class builds the table together before students work in pairs.

What to look for

Present students with two different approaches to debugging a faulty 'while' loop: one using a trace table and another using print statements. Ask: 'Which method would you use for this specific loop, and why? What are the advantages of your chosen method for finding this type of error?'

• Understand
• Analyze
• Evaluate
• Relationship Skills
• Self-Management

Activity 03

• Jigsaw
• 30 min · Whole Class

Whole Class: Live Debug Projection

Project a simple program with a hidden logic error on the board. Class suggests tests step by step, votes on predictions, and watches live execution. Reveal and correct as a group, noting the strategy used.

Critique a given piece of code to identify potential logic flaws in its selection structure.

Facilitation Tip

During Live Debug Projection, freeze the projection after each print statement output and ask students to predict the next state before you reveal the next line.

What to look for

Give each student a small code snippet with a logic error in a selection structure. Ask them to write down: 1. The specific line number where the logic error occurs. 2. A brief explanation of why it is a logic error. 3. How they would fix it.

• Understand
• Analyze
• Evaluate
• Relationship Skills
• Self-Management

Activity 04

• Jigsaw
• 25 min · Individual

Individual: Checklist Debug Station

Students receive a checklist of debugging steps and a buggy conditional program. They work solo to apply steps, log findings, then pair-share results. Extend by rewriting the fixed code.

Explain a systematic approach to finding a logic error in a conditional statement.

Facilitation Tip

During Checklist Debug Station, model how to tick off each checklist item aloud so students internalize the systematic procedure.

What to look for

Provide students with a short program containing a clear logic error in an 'if' statement (e.g., checking if a score is greater than 100 when it should be greater than or equal to 100). Ask them to identify the incorrect condition and rewrite it correctly.

• Understand
• Analyze
• Evaluate
• Relationship Skills
• Self-Management

A few notes on teaching this unit

Teach debugging as a protocol, not a puzzle. Use think-alouds to show how experienced programmers pause at each step, record variable states, and compare against the plan. Avoid rushing to ‘fix’ student code; instead, ask them to explain their observation first. Research shows that students trained to trace code manually transfer this skill to new problems better than those who rely on automated hints.

Successful learning looks like students confidently using trace tables or print statements to isolate mismatches between expected and actual outputs. They should articulate why a condition failed and how to adjust it, not just ‘make it run without errors.’

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Watch Out for These Misconceptions

• During Pair Swap: Logic Bug Hunt, watch for students who swap partners and immediately start changing code without explaining their reasoning or the expected behavior.

  Pause the class after two minutes and ask each pair to state one hypothesis about the bug before touching the keyboard. Use a sentence stem: ‘I think the bug is on line ___ because ___.’

• During Trace Table Challenge, watch for students who fill the table row-by-row without pausing to check if the result matches the specification.

  Insert a ‘Checkpoint’ column in the trace table where students write whether the output matches the expected result for that step. Circulate and ask, ‘Does this value align with the program’s goal here?’

• During Live Debug Projection, watch for students who assume the bug is obvious once the program runs, without analyzing print outputs.

  After each print statement, freeze the screen and ask students to write down what they see versus what they expected, using a simple T-chart on mini-whiteboards.

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Methods used in this brief

• Jigsaw