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KS4: Sexually Transmitted Infections

In this lesson plan, a classroom-based activity is used to demonstrate how easily sexually transmitted infections (STIs) can be transmitted. Using chlamydia as an example, this lesson helps students to understand how quickly STIs can spread and the potential consequences of infection.

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Learning objectives
All students will:
  • Understand that infection can be spread easily through sexual contact
  • Understand what students can do to protect themselves against STIs
  • Know that not everyone with an STI has symptoms
  • Understand that non-barrier forms of birth control do not protect against STIs
Most students will:
  • Understand how easily infections like chlamydia can spread among young people
  • Begin to explore effective communication surrounding condom use
Background Information

STIs are contracted by having close sexual contact with someone who is already infected. Some STIs can be treated and cured with antibiotics whereas others cannot. Many symptoms of incurable STIs can be treated to make them easier to live with. There are over 25 different STIs.

Anyone can contract an STI. Most people who contract an STI do not know that the person they have sexual contact with is infected. When discussing sexual health with students, it is important everyone feels comfortable, safe, and heard. Ideas for ground rules are available in the Teacher Guidance for the Key Stage 4 pack.

In this lesson plan, students explore how quickly sexually transmitted infections can spread between people and how to prevent this through the use of condoms. They are introduced to some common misconceptions around STIs and encouraged to identify legitimate sources of information to address these. In addition, the lesson plan includes activities to support students in discussing and negotiating safer sex practices.

Main activity:
  • Test tube experiment
Main Activity video
Extension activities:
  • Looking for legitimate sources of information
  • Safer sex: risks, communication and information
  • Raising awareness about gonorrhoea
  • Condom negotiation
  • Sexual health bingo
  • Guest speaker
Curriculum links


  • Working scientifically
  • Biology


  • Reading
  • Writing


  • Health and prevention
  • Intimate and sexual relationships
  • Sexual health
Supporting Materials
Teacher sheets
KS4 STIs teacher guidance
KS4 Test tube experiment - video transcript
TS1 STI misconceptions
TS2 Sexual health bingo caller cards
Student worksheets
SW1 Spread of STIs test tube experiment
SW2 STI misconceptions
SW3 Let's talk worksheet
SW4 Sexual health bingo
SW5 STI quiz
Student handouts
SH1 Let's talk about condoms
SH2 Let's talk about condoms