Lesson Overview
Students write their first loop programs using block-based coding to create repeating geometric art patterns. They discover how loops reduce code repetition, predict the output of loop programs, and debug broken loop sequences — aligned to CSTA 1B-AP-10 and 1B-AP-11.
Learning Objectives
Students will be able to:
- Explain what a loop is and why programmers use them
- Write a loop that repeats a sequence of steps a specific number of times
- Predict the output of a loop program before running it
- Identify and fix a bug in a loop program
Lesson Phases (5E Model)
- 1Stand up: 'We're going to follow an algorithm. Ready? Step right, step left, clap, clap. Now repeat that 4 times.'
- 2Students perform it — ask: 'Was it easier to remember all 16 steps, or just repeat the pattern 4 times?'
- 3Connect to programming: 'That's a loop! Instead of writing the same steps over and over, we tell the computer to REPEAT.'
- 4Show two versions of the same program on the projector — one with copy-pasted blocks, one with a loop. Ask: 'Which would you rather write?'
Assessment Strategies
Loop Prediction Worksheet
Scored on accuracy of predictions — demonstrates loop comprehension before coding
Algorithm Art Program
Evaluated on: working loop, correct iteration count, and creative pattern
Gallery Sticky Note
Formative check — can students identify loop iteration count in peers' code?
Extension Activities
- →Explore nested loops — a loop inside a loop (Code Academy Level 2 content)
- →Math connection: calculate the number of degrees per turn for any regular polygon
- →Challenge: create animated loop art where the pattern changes color each iteration
- →Real-world connection: find examples of loops in everyday technology (traffic lights, music playlists)
At a Glance
Grade BandGrades 3-5
Duration50 min
Group SizeIndividual or pairs
DifficultyBeginner
SubjectComputer Science
Lesson Model5E Instructional Model
Materials
- Devices with access to Code Academy or Scratch1 per student/pair
- Loop prediction worksheets (unplugged)1 per student
- Graph paper for pattern sketching1 per student
- Colored pencils or markers1 set per student
- Algorithm Art Gallery wall spaceClass shared
Key Vocabulary
- Loop
- A programming instruction that repeats a set of steps a certain number of times
- Iteration
- One time through a loop — if a loop runs 5 times, it has 5 iterations
- Pattern
- A design or sequence that repeats in a predictable way
- Bug
- A mistake in a program that causes it to behave incorrectly
- Debug
- Finding and fixing bugs in a program
Digital Tools
- →Code Academy — Loops & Repetition Lessons
- →Code Academy Scratch Integration
