Understanding Algorithms

Overview

This 45-minute session introduces Year 9 students to the concept of algorithms within the “Programming Fundamentals with Python” unit. The lesson aligns with the National Curriculum for England’s Computing Programme of Study, specifically the aim to “understand and apply the fundamental principles and concepts of computer science, including abstraction, decomposition, logic, algorithms;” (Key Stage 3 Computing, England). Students will define algorithms and learn to articulate simple algorithms in plain English, developing skills in decomposition and logical sequencing.

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Learning Objectives

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

• Define what an algorithm is, consistent with the National Curriculum key concept that “an algorithm is a precise step-by-step set of instructions” (Program of Study, KS3).
• Express simple algorithms clearly and precisely in plain English.
• Apply decomposition to break down a given task into a sequence of step-by-step instructions.
• Understand the importance of logical order and clarity in algorithms.

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National Curriculum References

• Computing KS3 (Years 7–9) – Programme of Study:
  • “Understand and apply the fundamental principles and concepts of computer science, including abstraction, decomposition, logic, algorithms;”
  • “Design, use, and evaluate computational abstractions that model the state and behaviour of real-world problems and physical systems.”
  • “Design, write and debug programs that accomplish specific goals.”
• Computing KS2 revision (to recap earlier understanding):
  • Recognise that programming projects can be broken down into smaller parts.
• Develops computational thinking skills as promoted in the DfE Computing Guidance.

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Resources Required

• Whiteboard and markers
• Printed scenario/task cards with simple real-world problems (20 cards – 1 per student)
• Blank worksheet for algorithm writing (1 per student)
• Timer/stopwatch
• Sticky notes or small paper slips

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Lesson Structure

1. Starter Activity (5 minutes)

Quick Think-Pair-Share

• Pose the question: “What is an algorithm?”
• Students think silently for 1 minute, then discuss in pairs for 2 minutes.
• Select 3 pairs to share their definitions aloud.
• Teacher consolidates and writes a clear definition on the board:
  “An algorithm is a precise sequence of steps or instructions designed to perform a task or solve a problem.”

Rationale: Engages prior knowledge, encourages collaboration, and activates language skills to articulate abstract concepts early.

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2. Main Teaching Activity (15 minutes)

a) Explanation & Modelling (7 minutes)

• Teacher presents brief examples of algorithms in everyday life, e.g., making a cup of tea or tying shoelaces.
• Demonstrate how to write the steps in plain English using simple sequencing and clarity (avoid ambiguous instructions). Write example on whiteboard.
• Highlight key algorithm features: clear, unambiguous, ordered steps; inputs and outputs implicit; no missing steps.

b) Group Task: Decompose and Write (8 minutes)

• Split class into 5 groups of 4.
• Provide each group with a different simple real-world task on a card (e.g., “Tie your shoelaces,” “Prepare a peanut butter sandwich,” “Plant a seed in a pot,” “Get dressed for school,” “Make a paper airplane”).
• Each group discusses and writes their algorithm in plain English on worksheet. Emphasise step-by-step precision and logical order.
• Circulate and assist groups with clarifying ambiguous steps.

Rationale: Practical application of defining and expressing algorithms aids understanding and gives context to abstract concepts, addresses KS3 focus on modelling real-world problems through computational abstractions.

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3. Consolidation Activity (10 minutes)

Algorithm Exchange & Peer Review

• Groups exchange their written algorithms with another group.
• Each group reads the received algorithm and tries to follow the steps; they identify any parts that are unclear or missing.
• Use sticky notes to add improvement suggestions or identify unclear parts on the algorithm sheet.
• Brief class discussion on challenges, showing how algorithm clarity and order matter to successful execution.

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4. Plenary & Formative Assessment (10 minutes)

Individual Reflection and Quiz

• Students complete a short written reflection on:
  • “What makes a good algorithm?”
  • “Why is it important to break a task down into ordered steps?”
• Follow with a quick-fire verbal quiz (teacher-led):
  • What is an algorithm?
  • Give an example of an algorithm.
  • Why must steps be in logical order?
  • How can breaking down tasks help programming?

Assessment: Using the written reflection and quiz responses, assess understanding and address misconceptions.

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Differentiation Support

• For Lower Ability: Provide simplified task cards and sentence starters (e.g. “First I will… Next I will…”).
• For Higher Ability: Challenge with creating an algorithm for an unfamiliar task or asking how code could represent these algorithms later in Python.
• Offer verbal aids and peer support when required.

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Homework / Extension

• Ask students to write an algorithm in plain English for a morning routine at home (break down into detailed steps).
• Encourage them to think about how they would translate this later into Python code.

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Teacher Notes and Tips

• Emphasise that algorithms are not the same as code but the blueprint for writing code - this will help prepare students for future lessons on coding in Python.
• Use everyday familiar tasks to make the abstract concept relatable to 13-14 year olds.
• Make the peer review constructive and friendly, reinforcing teamwork and critical thinking.
• Keep the language accessible and consistent with KS3 computing vocabulary.

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This lesson plan connects clearly to the national curriculum, instils foundational programming skills through algorithmic thinking, and nurtures communication, reasoning, and collaboration skills essential to technology education.