Events and Actions in Programs — Year 3 Lesson Plan
National Curriculum: Computing KS2 — design, write and debug programs that accomplish specific goals; use sequence, selection and repetition in programs; work with variables and various forms of input and output
Overview
Pupils extend their Scratch programming skills by exploring events and actions — how programs respond to user input such as key presses, mouse clicks, and broadcasts. They learn to coordinate multiple sprites using broadcast and receive blocks, and apply their knowledge by designing and building a simple interactive program. The lesson reinforces decomposition: breaking a complex program into sprite-by-sprite tasks.
Learning Objectives
- Explain what an event is and give examples from everyday computing.
- Use event blocks in Scratch to make sprites respond to different types of input.
- Use broadcast and receive blocks to coordinate actions across multiple sprites.
- Design and build a simple interactive program using events, sequences, and loops.
Key Vocabulary
Suggested Lesson Structure
Events in everyday life: press a button in a lift — doors open (event → action). A smoke alarm detects smoke — an alarm sounds. Ask pupils for three more examples. Establish: computers are full of events. Every time you press a key, click the mouse, or touch a screen, you are triggering an event. Open Scratch: 'When green flag clicked' is the most familiar event — but there are many more.
Explore the Events palette in Scratch: When green flag clicked, When key pressed, When this sprite clicked, When I receive. Build a live demo: sprite 1 plays a sound when spacebar is pressed; sprite 2 moves when the right arrow key is held. Then introduce broadcast: 'When green flag clicked → wait 3 seconds → broadcast go'. Sprite 2 has 'When I receive go → move'. Explain: broadcast lets sprites communicate — one sprite's action triggers another's response. This is how complex programs are coordinated.
Pupils open a starter Scratch project with two sprites and three broken event handlers. Task: fix the events so that pressing Space makes Sprite 1 jump, clicking Sprite 2 changes its costume, and pressing 'g' broadcasts a message that moves Sprite 1 to a new position. Teacher circulates: 'What event should trigger this? Is it the right event block?'
Pupils design and build a mini interactive scene: at minimum two sprites, at least three different events, and one use of broadcast and receive. They complete a planning sheet (event → action for each sprite) before coding. Examples: a cat that meows when clicked, a fish that swims when arrow keys are pressed, a sun that rises on key press and broadcasts 'morning' to wake a sleeping sprite.
Two or three pupils demo their project. For each, the class identifies the events and actions: 'What was the trigger? What was the handler?' Summarise: events make programs interactive. Look ahead — next year, selection (if/else) will let programs make decisions based on conditions, making them even more responsive.
Common Misconceptions
- Putting all code under 'When green flag clicked' — this means everything runs at the start and nothing responds to input during the program, so it is not truly interactive.
- Broadcast only works within one sprite — broadcasts are sent to all sprites; any sprite can listen for and respond to any broadcast message.
Prior Knowledge
Pupils should already be able to:
- Confident use of sequences in Scratch, including moving sprites and playing sounds.
- Understanding of loops and iteration from the Sequences and Loops unit.
- Ability to debug simple programs by reading code and tracing execution.
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