PBS
Nova: How Is Sex Determined?
This site focuses on the first 16 weeks of embryo development when the sex of the child is determined.
OpenStax
Open Stax: Anatomy and Physiology: Male and Female Reproductive Development
Find out about the development and hormonal changes associated with reproductive development for both males and females.
National Cancer Institute at the National Institutes of Health
Seer Training Modules: Introduction to the Reproductive System
Self-guided learning activity where students learn about the structure and function of the male and female reproductive systems. There is a short quiz at the end of the lesson to check for understanding.