Lesson 2: Decomposition

Pupils apply their understanding of decomposition to a real world task before analysing Code from Scratch to figure out what it might do

Before the lesson

Download classroom resources

Learning objective

  • To understand what decomposition is and how to apply it to solve problems

National curriculum

Pupils should be taught to:

  • Design, write and debug programs that accomplish specific goals, including controlling or simulating physical systems; solve problems by decomposing them into smaller parts
  • Use logical reasoning to explain how some simple algorithms work and to detect and correct errors in algorithms and programs

Success criteria

Cross-curricular links

Attention grabber

Main event


Pupils needing extra support: Should be encouraged to identify two or three key features for the game and think about how to code them.


Pupils working at greater depth: Should be encouraged to think about extra features they could add into their game and how they might code them, e.g. adding further obstacles for the bug to bump into or making their bug bigger or smaller.

Wrapping up

Assessing pupils' progress and understanding


Created by:
Cat Lamin,  
Computing specialist
Cat was a committed primary school teacher for twelve years. After starting her independent consultancy ‘Crossover Solutions’ she has travelled to Argentina, Brazil and America to share her wealth of knowledge of computer science with other teachers. Her enjoyment for…
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