Code with Scratch

Curriculum Alignment

Key Stage 3 (KS3) - Computing

• Subject Content: The UK National Curriculum outlines that students in lower KS3 should be able to design, use, and evaluate computational abstractions that model the state and behaviour of real-world problems and physical systems.
• Specific Area: Designing, writing, and debugging programs using a visual programming language (Scratch).

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Learning Objectives

By the end of the lesson, students will be able to:

1. Understand the concept of a loop and how it can be used in coding to repeat commands.
2. Use Scratch blocks to create a simple animation incorporating loops.
3. Debug errors in their Scratch programs.
4. Begin thinking computationally by breaking problems down into smaller tasks.

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Resources Needed

• Computers/laptops with Scratch installed or access to the Scratch website.
• Interactive whiteboard or projector.
• Scratch quick-reference guide (printed or displayed).
• Pre-prepared Scratch template file (e.g., a character and a background ready to work on).

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Lesson Structure

1. Starter Activity (5 minutes)

• Goal: Warm-up and recall prior knowledge.
• Activity: Pose the question: “What problems do computers solve, and how do they do it?” Students brainstorm for 1-2 minutes, shouting out answers.
• Facilitate a quick discussion introducing the idea of repetition in solving problems (like repetitive motions, loops for efficiency).
• Show a simple program on Scratch using the ‘when green flag clicked’ and a motion command without a loop. Manually repeat the block 4-5 times to show inefficiency. Tease the idea of loops as a solution but don’t explain yet.

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2. Explanation & Teacher-Led Demonstration (10 minutes)

Focus: Introducing Loops in Scratch

• Start by defining what a loop is: “A way to repeat actions or commands without writing them multiple times.” Use relatable examples like brushing teeth or taking steps.
• Open the pre-prepared Scratch project on the whiteboard. This has:
  • A sprite (e.g., a cat).
  • A simple background.
• Demonstrate how to use a loop:
  1. Use [Motion] blocks (e.g., Move 10 Steps) and run the program without a loop.
  2. Add a repeat block and place the motion command inside.
  3. Challenge students: "What do you think will happen when I run this now?"
  4. Play and explain: "The loop repeats the steps automatically, making our program efficient."

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3. Guided Practice (15 minutes)

Goal: Students create their own animation using loops.

Instructions:

1. Ask students to open Scratch and create a new project.
2. Give them a step-by-step task:
   • Select a sprite (choose a character of their choice).
   • Select a backdrop.
   • Add motion commands, using a loop to make the sprite move repetitively (e.g., make the sprite glide in a square, or bounce forever).
3. Provide extension tasks for faster learners:
   • Add a sound effect to the loop.
   • Use the ‘forever’ loop instead of the repeat loop and explain how they differ.

Tips for Teachers:

• Walk around the room, helping where necessary.
• Encourage peer collaboration for those stuck. Pair struggling students with confident coders.

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4. Debugging Challenge (7 minutes)

• Present the class with a faulty Scratch program on the whiteboard (e.g., a sprite moves chaotically, or the loop doesn’t run correctly).
• As a group, debug the program by identifying what’s wrong. Use reasoning (e.g., incorrect block placement, wrong number in the loop).
• Pose questions like: "What would happen if I changed this number?" or "Why doesn't this loop work as expected?"

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5. Plenary (8 minutes)

• Reflection Discussion: Use the following scaffolding questions:
  • "What is the purpose of using loops in coding?"
  • "What tasks became easier when you used a loop today?"
• Draw out computational thinking skills: problem decomposition, testing, and debugging.
• Student Challenge: Give them a "coding riddle" for homework (e.g., "How would you make a sprite move in a circle using loops?").

Finally, ask students to share one thing they learned in the lesson or found exciting.

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Differentiation

• For Lower-Ability Students: Provide a simplified project file they can edit directly (e.g., basic motion blocks with a loop already added). Pair them with capable students for peer support.
• For Higher-Ability Students: Encourage experimentation with additional blocks (e.g., sounds, conditional statements, or changing sprite costumes).

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Teacher Assessment

1. Observe student engagement during independent work and debugging challenges.
2. Informal questioning during guided practice.
3. Review students’ final projects and note who uses loops successfully.

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Homework/Extension

Create a Scratch project at home where a sprite repeats a motion (e.g., spinning, bouncing, or gliding) using both a repeat block and a forever block. Prepare to explain the differences in their next lesson.