Computing · Year 1 · Algorithms and the Unplugged World · Autumn Term

Finding and Fixing Errors (Debugging)

Students are introduced to the concept of debugging by identifying and correcting mistakes in simple physical sequences or instructions.

• National Curriculum Attainment Targets
• KS1: Computing - Algorithms
• KS1: Computing - Debugging

About This Topic

Debugging introduces Year 1 students to finding and fixing errors in simple instructions, using physical sequences like movement chains or block arrangements. Students follow sets of steps, notice when results do not match expectations, and correct mistakes, directly meeting KS1 Computing standards for algorithms and debugging. Key questions focus on recognising errors, identifying specific problems, and predicting outcomes after fixes, building confidence in logical steps.

This topic connects computational thinking to everyday routines, such as correcting a jumbled morning routine or game rules. It develops skills in testing instructions, persistence through trial and error, and precise communication, which support later programming units and cross-curricular links to maths sequences or PE routines.

Active learning suits debugging perfectly because students physically enact buggy instructions, experience unexpected results firsthand, and collaborate to test fixes. This hands-on approach turns abstract error-spotting into a playful, memorable process that encourages resilience and peer support.

Key Questions

1. How do you know when something has gone wrong with a set of instructions?
2. Can you spot what went wrong with these instructions?
3. What do you think will happen once we fix this mistake?

Learning Objectives

• Identify the specific instruction that causes an error in a given physical sequence.
• Explain why a particular step in a sequence is incorrect.
• Demonstrate a corrected sequence of instructions to achieve a desired outcome.
• Compare the original, incorrect sequence with the corrected sequence.

Before You Start

Following Simple Instructions

Why: Students need to be able to understand and execute a basic set of commands before they can identify when those commands are incorrect.

Identifying Objects

Why: To debug instructions involving specific items (like colored blocks or shapes), students must be able to accurately identify those objects.

Key Vocabulary

Algorithm	A set of step-by-step instructions for completing a task or solving a problem.
Bug	A mistake or error in a set of instructions that prevents it from working correctly.
Debugging	The process of finding and fixing errors, or bugs, in a set of instructions.
Sequence	The order in which instructions are performed.

Watch Out for These Misconceptions

Common Misconception

Errors are always obvious and large.

What to Teach Instead

Small changes, like swapping two steps, can cause big failures. Physical testing reveals these, as students see minor tweaks lead to correct outcomes. Group trials help compare results and build error-detection skills.

Common Misconception

Instructions work perfectly first time.

What to Teach Instead

All instructions need testing and fixing. Acting out sequences shows repeated checks are normal, fostering a growth mindset. Peer feedback during activities highlights overlooked issues effectively.

Common Misconception

There is only one right way to fix an error.

What to Teach Instead

Multiple solutions exist for the same problem. Collaborative debugging lets students propose and test varied fixes, valuing creativity. This reduces frustration and encourages experimentation.

Active Learning Ideas

Pairs Activity: Human Robot Debugging

One student acts as a 'robot' following partner's oral instructions to navigate a space with obstacles. Switch roles after observing errors like missed turns. Pairs discuss and revise instructions, then retest for success.

30 min·Pairs

Small Groups: Sequence Card Sort

Provide cards showing a buggy sequence, such as building a tower with wrong block order. Groups identify the error through discussion, reorder cards, and test by stacking physically. Record before-and-after sequences on paper.

25 min·Small Groups

Whole Class: Toy Path Challenge

Project a path for toy vehicles with deliberate errors like sharp turns. Class votes on problems, suggests fixes, and tests one at a time with the toy. Chart successful paths on the board.

35 min·Whole Class

Individual: Personal Routine Fix

Students write or draw their morning routine with one planted error. Self-check by acting it out, note the issue, and rewrite correctly. Share one fix with the class.

20 min·Individual

Real-World Connections

• When following a recipe to bake a cake, a chef might realize they added salt instead of sugar. They must identify the incorrect step and correct it to ensure the cake is edible.
• A traffic light system uses algorithms to control traffic flow. If a light stays red too long, engineers must debug the system to prevent traffic jams.
• Robot toy instructions can sometimes be confusing. A child might follow the steps to make a robot move, but if it spins instead of walking, they need to find the wrong step and fix it.

Assessment Ideas

Quick Check

Present students with a simple 3-step physical sequence (e.g., '1. Stand up. 2. Clap hands. 3. Sit down.'). Introduce one deliberate error (e.g., '1. Stand up. 2. Sit down. 3. Clap hands.'). Ask students to perform the sequence and then point to the step that caused the unexpected result.

Discussion Prompt

Show students a visual representation of a buggy instruction set, like a set of arrows for drawing a shape that leads to the wrong shape. Ask: 'Which arrow is pointing the wrong way? How should we change it so it makes the correct shape?'

Exit Ticket

Give each student a card with a simple 2-step instruction (e.g., '1. Pick up the red block. 2. Put it on the blue block.'). Then provide a 'buggy' version (e.g., '1. Pick up the blue block. 2. Put it on the red block.'). Ask students to write one sentence explaining what went wrong and one sentence explaining how to fix it.

Frequently Asked Questions

How do you introduce debugging to Year 1 computing?

Start with familiar physical tasks, like directing a friend to draw a shape with vague instructions that fail. Guide students to spot mismatches between intent and result, then fix collaboratively. Use visuals like arrow cards to represent steps, reinforcing that precise instructions matter in algorithms.

What unplugged activities work best for debugging?

Human robot games, sequence card sorts, and toy path challenges engage kinesthetic learners. These let students test instructions physically, discuss errors in pairs or groups, and iterate fixes. Keep setups simple with classroom items to maintain focus on the process over materials.

How does active learning benefit debugging lessons?

Active methods make errors tangible: students feel frustration from buggy steps, then joy in fixes, building resilience. Physical enactment and peer testing reveal subtle issues faster than passive explanation. Collaborative tweaks promote communication and deeper understanding of algorithms in real time.

How does debugging link to other Year 1 curriculum areas?

It strengthens maths pattern work through sequence fixes and PE via movement instruction precision. Links to English story sequencing encourage checking logical flow. Across subjects, it teaches systematic problem-solving, preparing for digital tools while embedding computational thinking early.