Computing · Year 3 · Sequence and Structure: Programming with Sprites · Autumn Term

Finding and Fixing Bugs (Debugging)

Developing strategies to find and fix errors in code through systematic testing.

• National Curriculum Attainment Targets
• KS2: Computing - Programming
• KS2: Computing - Debugging

About This Topic

Finding and fixing bugs means students develop strategies to spot and correct errors in their code through careful testing. In Year 3, this builds on sprite programming where pupils write sequences for characters to move, repeat actions, or respond to events. They learn to test code step by step, predict outcomes, and isolate problems, such as a sprite moving in the wrong direction due to a misplaced block or an endless loop from faulty repetition.

This topic aligns with KS2 Computing standards for programming and debugging, fostering persistence and logical thinking. Students justify why errors are normal in coding, analyse single code blocks for issues, and evaluate calm problem-solving methods. These skills transfer to maths pattern work and everyday troubleshooting, like fixing a faulty toy circuit.

Active learning shines here because students actively run, tweak, and retest code in real time. Pair work on shared programs encourages verbalising thought processes, while group challenges turn frustration into shared success, making abstract debugging concrete and building resilience.

Key Questions

1. Justify why 'failing' is a vital part of the programming process.
2. Analyze strategies to isolate a single block of code causing a bug.
3. Evaluate different approaches to staying calm when code does not work as expected.

Learning Objectives

• Identify specific code blocks that cause a sprite to behave unexpectedly.
• Explain why testing code incrementally helps in locating errors.
• Analyze the impact of a single incorrect code block on a sprite's sequence of actions.
• Evaluate strategies for remaining calm and persistent when debugging code.
• Justify the importance of errors as learning opportunities in programming.

Before You Start

Introduction to Sprite Programming

Why: Students need to be familiar with basic sprite movement commands and event handling before they can identify and fix errors within them.

Understanding Sequences

Why: A foundational understanding of how instructions are executed in order is necessary to recognize when a sequence is broken by a bug.

Key Vocabulary

bug	An error or fault in a computer program that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.
debugging	The process of finding and fixing errors, or bugs, in computer code.
sequence	A set of instructions that are followed in a specific order to achieve a result.
loop	A programming structure that repeats a sequence of instructions until a specific condition is met.
test	To run a program or part of a program to check if it works correctly and to find any bugs.

Watch Out for These Misconceptions

Common Misconception

Bugs mean I am bad at coding, so I should start over.

What to Teach Instead

Errors are part of every programmer's process; systematic testing shows most bugs are small fixes. Active pair reviews help students see others' code succeed after tweaks, normalising trial and error while building calm persistence.

Common Misconception

The computer made the mistake; my code was perfect.

What to Teach Instead

Code runs exactly as written, so bugs come from human instructions. Hands-on re-running with predictions reveals mismatches between intent and output. Group debugging stations reinforce this by comparing code side by side.

Common Misconception

Fix bugs by changing everything randomly until it works.

What to Teach Instead

Effective debugging isolates one change at a time through testing. Station rotations with code cards teach prediction before tweaks, helping students track what caused success and avoid random guesses.

Active Learning Ideas

Pair Debug Challenge: Sprite Maze

Provide buggy code for a sprite to navigate a maze. Pairs predict what will happen, run the code, note the exact failure point, and fix one block at a time. They swap with another pair to test fixes and explain changes.

30 min·Pairs

Bug Hunt Stations: Code Cards

Set up stations with printed code snippets on cards showing common errors like wrong sequences or loops. Small groups test each on devices, circle the bug, and rewrite correctly. Rotate stations and share one fix per group.

45 min·Small Groups

Whole Class Debug Demo: Live Prediction

Project a buggy sprite program. Class predicts behaviour, you run it to reveal the bug, then vote on fixes. Implement student ideas live, discuss why each works or fails, and log strategies on a shared board.

20 min·Whole Class

Individual Test Log: Personal Program

Students create a simple sprite dance, introduce a deliberate bug, then log tests: prediction, outcome, change made. They repeat until fixed, reflecting on patterns in their errors.

25 min·Individual

Real-World Connections

• Video game developers at companies like Nintendo constantly debug their games. For example, they might fix a bug where a character falls through the floor or an enemy does not respond correctly, ensuring a smooth player experience.
• Software engineers building apps for smartphones, such as those used by delivery drivers for companies like Amazon, must debug code to ensure navigation features work accurately and orders are processed without errors.

Assessment Ideas

Quick Check

Provide students with a simple sprite program containing one obvious bug (e.g., a sprite moving left instead of right). Ask them to run the code, identify the incorrect block, and explain what change they would make to fix it.

Discussion Prompt

Pose the question: 'Imagine your sprite is stuck in a loop, repeating the same action forever. What are three steps you could take to figure out which part of your code is causing the problem?' Facilitate a class discussion, encouraging students to share their strategies.

Exit Ticket

Give each student a card with the statement: 'When my code doesn't work, I feel...'. Ask them to complete the sentence and then write one strategy they can use to help them stay calm and keep trying to fix the bug.

Frequently Asked Questions

How do you introduce debugging strategies in Year 3 sprite programming?

Start with simple, predictable bugs like reversed move blocks or missing forever loops. Model systematic testing: run code, observe output, hypothesise the issue, test one fix. Use visual block interfaces to make changes obvious, and celebrate 'eureka' moments to build confidence over 3-4 lessons.

What are common bugs in Year 3 sprite sequences?

Frequent issues include blocks in wrong order causing unexpected paths, repetition without stops leading to endless actions, or event triggers misplaced so sprites ignore clicks. Teach isolation by commenting out blocks one by one, a low-frustration method that reveals the culprit quickly.

How can active learning help students with debugging?

Active approaches like pair prediction-run-fix cycles make debugging collaborative and low-stakes. Students verbalise steps aloud, reducing solo frustration, while stations or relays expose multiple bugs for pattern spotting. This hands-on iteration mirrors real programming, boosting resilience and turning 'failure' into vital learning.

How to help students stay calm when code fails?

Frame bugs as puzzles, not failures, with class chants like 'test, tweak, try again'. Use timers for short debug bursts to prevent overwhelm, and pair stronger coders with peers for encouragement. Reflection logs at lesson end highlight progress, reinforcing that persistence pays off.