Activity 01
Pairs: Buggy Code Challenge
Provide pairs with printed or digital sequential programs containing one error, like wrong block order. Pairs predict output, run the code, identify the bug, fix it, and retest. They then swap with another pair to verify the solution.
Explain common reasons why a sequential program might not work as expected.
Facilitation TipDuring Buggy Code Challenge, circulate and ask pairs to predict the sprite’s final position before running the program to build anticipation and focus on sequence logic.
What to look forProvide students with a simple Scratch program that has one clear bug (e.g., a sprite moving in the wrong direction). Ask them to run the program, identify the bug, and write down what the incorrect command or sequence is.
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Activity 02
Small Groups: Multi-Bug Hunt
Distribute code snippets with 2-3 errors to small groups. Groups trace steps on paper first, then code and test digitally, logging each fix with evidence. Present one fix to the class for feedback.
Critique a given program to identify where an error might be located.
Facilitation TipIn Multi-Bug Hunt, assign each group a distinct color highlighter so students visibly mark each bug they find, making invisible errors tangible and trackable.
What to look forPresent a short, flawed program to the class. Ask: 'Where in this sequence do you think the problem lies and why?' Facilitate a discussion where students point to specific blocks and explain their reasoning for suspecting an error there.
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Activity 03
Whole Class: Prediction Debug
Project a buggy sequence program. Class predicts output via show-of-hands vote, run it to reveal failure, then suggest and test fixes one-by-one on the board. Discuss why each test matters.
Justify the importance of testing a program after making changes.
Facilitation TipDuring Prediction Debug, pause the class after each block and ask for a thumbs-up or sideways for correct or uncertain predictions to surface misconceptions in real time.
What to look forGive each student a printout of a program with a logic error. Ask them to draw an arrow pointing to the line or block they believe is causing the problem and write one sentence explaining why they think it's the source of the bug.
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Activity 04
Individual: Debug Journal
Give each student a personal buggy program. They document steps: predict, run, hypothesise error, fix, retest. Review journals in plenary to share common fixes.
Explain common reasons why a sequential program might not work as expected.
Facilitation TipIn Debug Journal, demonstrate how to sketch a simple flowchart of the corrected sequence so students connect linear steps to visual problem-solving.
What to look forProvide students with a simple Scratch program that has one clear bug (e.g., a sprite moving in the wrong direction). Ask them to run the program, identify the bug, and write down what the incorrect command or sequence is.
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Generate Complete Lesson→A few notes on teaching this unit
Teach debugging as detective work: model tracing code with your finger, narrating each step aloud and pausing at possible pitfalls. Avoid rushing to solutions; instead, ask learners to explain why a block might be out of place before editing. Research shows that structured verbalization during debugging strengthens metacognitive control, and collaborative talk scaffolds these explanations before students work alone.
By the end of the sequence, students will predict outputs, locate bugs without guessing, and explain fixes using precise vocabulary. They will also test changes methodically and justify their testing choices to peers.
Watch Out for These Misconceptions
During Buggy Code Challenge, watch for students who assume every error is a typing mistake and immediately reach for the keyboard instead of tracing the sequence.
Remind pairs to pause, run the program mentally block-by-block, and mark each step on paper before making any changes.
During Multi-Bug Hunt, watch for students who declare the program fixed after fixing one bug even though others remain.
Have groups add a checklist to their highlighters and tick each bug they find; only when all ticks match the original list do they call it fixed.
During Prediction Debug, watch for students who change the code before explaining why the sequence fails.
Freeze the class after each prediction round and require students to write a one-sentence explanation of the expected outcome before running the code.
Methods used in this brief