KS4: Sexually Transmitted Infections In this lesson plan, a classroom-based activity is used to demonstrate how easily 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. Scroll down for more information and to download the resources. Download the complete lesson Understand that infection can be spread easily through sexual contact Understand what students can do to protect themselves agai...