Python Decision Making

Overview

Duration: 60 minutes
Class size: 25 students
Unit: Python Decision Making (Lesson 1 of 1)
Year group: Year 8 (age 12-13)
Subject: Computing / Computer Science – Other
National Curriculum Link:

• Key Stage 3 Computing Programme of Study (Years 7-9, DfE 2013)
• Relevant aims:
  • Understand and use selection statements to control the flow of programs.
  • Use logical reasoning to explain how some simple algorithms work.
  • Use variables, inputs, and operators to make decisions in programs.

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Learning Objectives

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

1. Explain the purpose of decision making in programming (e.g., how programs react differently based on conditions).
2. Demonstrate understanding of if, if-else, and nested if statements in Python.
3. Apply comparison, arithmetic, and Boolean operators within selection statements to create simple decision-making programs.
4. Write and test Python programs that use user inputs to make decisions and produce different outputs accordingly.

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Curriculum Links

• National Curriculum for Computing (England, Key Stage 3):

  "Pupils should be taught to use selection in programs [for example, using IF, ELSE statements...] and iteration."

• Computing Programmes of Study, Years 7 to 9, Strand 2: Algorithms and Programming

• Computing Content Descriptor KS3:

  "Use two or more programming languages, at least one of which is textual, to solve a variety of computational problems; use sequences, selection, and iteration in programs; work with variables and various forms of input and output."

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Resources Needed

• Computers with Python 3 installed (preferably with IDLE or a simple IDE such as Thonny)
• Projector and screen for teacher-led demonstrations
• Printed handouts with simple program stubs (optional)
• Whiteboard and markers
• Sticky notes or mini-whiteboards for quick formative assessment
• Timer

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Lesson Structure

1. Starter (10 minutes) – Engaging Prior Knowledge & Introducing Concepts

• Activity: Class discussion: "What decisions do computers make?"
  • Teacher prompts with real-world examples (e.g., apps checking passwords, games reacting to user actions).
  • Write keywords on the board: Decision, Condition, True/False, If, Else.
• Quick introduction to decision making logic:
  • Use an everyday flowchart (e.g., "If it is raining, take an umbrella; else, don’t").
  • Link the flowchart concept to programming selection statements.

National Curriculum link: Developing logical reasoning and computational thinking (KS3 PoS)

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2. Main Teaching Input (15 minutes) – Explain if, if-else, nested if

• Demonstrate syntax using live coding:

  • Write a simple if statement example:

    if 10 > 5:  
        print("10 is greater than 5")  
    

  • Discuss indentation and its importance in Python.

• Explain using comparison operators (==, !=, <, >, <=, >=) and Boolean operators (and, or, not):

  • Show examples of each operator in conditional statements.

• Explain if-else structure:

  • Show example where program prints different messages depending on input age.

• Introduce nested if statements:

  • Write a small program that checks two conditions inside nested ifs (e.g., checking if a number is positive and even).

• Highlight use of user input:

  • Demonstrate input() function, casting input to int with int().

National Curriculum link: Use of operators, inputs and selection [KS3]

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3. Student Guided Practice (20 minutes) – Hands-On Programming Tasks

• Task 1: Simple Decision Program (Individual, 10 minutes)
  Students write a Python program that asks the user for their favourite number and tells them if it's greater than 10 or not.

  • Input: input() with int conversion
  • Use if-else with comparison operator
  • Example output: "Your number is greater than 10" or "Your number is 10 or less"

• Task 2: Nested Decision (Pairs, 10 minutes)
  Students work in pairs to create a program which:

  • Asks for a student's score (0-100).
  • Outputs:
    • "Distinction" if score >= 75
    • "Pass" if 40 <= score < 75
    • "Fail" if score < 40
  • Use nested if statements or multiple if-elif-else (teacher to confirm use of elif as an extension).

Teacher role: Circulate to support, ask probing questions about logic, syntax, and operator use.

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4. Plenary (10 minutes) – Reflect and Assess Understanding

• Class quiz using mini-whiteboards or sticky notes:

  • Teacher reads out Python code snippets or conditions and asks students to predict the output.
  • Examples include predicting output of if statements with Boolean operators or nested conditions.
  • Discuss answers interactively to consolidate learning.

• Peer explanation:

  • Select a few volunteers to explain the logic behind their nested if program to the class.

• Formative Assessment:

  • Quick “Exit Ticket” question (written or verbal):
    "Write a one-line explanation of when you would use an 'if-else' statement in programming."

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5. Differentiation

• For lower ability pupils:

  • Provide partially completed code snippets and focus on using simple if statements with clear boolean expressions.
  • Use flowcharts to help visualise decision logic before coding.

• For higher ability pupils:

  • Challenge them to add Boolean operators to combine conditions (e.g., check if number is positive AND even).
  • Encourage use of elif statements (beyond if-else) for more streamlined code.

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Assessment

• Ongoing formative assessment based on:

  • Accuracy of students’ written Python code during tasks.
  • Responses during plenary quiz.
  • Exit ticket explanation.

• Use of peer feedback during paired programming.

• Informal teacher notes on students’ ability to correctly use selection statements and operators.

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Extension Ideas (If time allows or for homework)

• Students modify programs to handle unexpected inputs (e.g., what if user types text instead of numbers?).
• Introduce the concept of Boolean expressions more deeply (truth tables).
• Create a simple text-based choosing-your-own-adventure game using nested if.

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Teacher Reflection Prompts

• Were all students able to grasp the concept of decision structures?
• Did examples sufficiently bridge the gap between everyday decision-making and programming logic?
• How effectively did students transfer their understanding into Python syntax?
• Could digital or physical visual aids be enhanced for next time?

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This plan ensures active participation, clear links to the KS3 national curriculum objectives for Computing, and provides a strong foundation for understanding programmatic decision making in Python.