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Cotmanhay Junior School

Safe, Happy Learning

Y3 Term 2 We are bug fixers

National curriculum content

Debug programs that accomplish specific goals.

Use logical reasoning to explain how some simple algorithms work and to detect and correct errors in algorithms or programs.


Lesson objectives

  1. Spotting and correcting off-by-one bugs
  2. Spotting and correcting performance bugs
  3. Spotting and correcting multi-thread bugs
  4. Spotting and correcting conceptual bugs
  5. Spotting and correcting arithmetical bugs
  6. Spotting and correcting resource bugs


What we want children to know

  • Correct ‘off-by-one’ errors in loops
  • Improve the performance of the circle-drawing program
  • Get the dialogue in the joke program to work in sequence
  • Experiment with the speed variable and other facts in the racing car simulator


What skills we want children to develop

  • A number of strategies for finding errors in programs
  • Build up resilience and strategies for problem solving
  • Increase their knowledge of and understanding of Scratch
  • Recognise a number of common types of bug in software
  • Debug programs that accomplish specific goals



algorithm, bugs, debug, instruction, program, script