The Hormone Factory is designed to teach kids about sex. It was approved by the Queensland Government to be used in Primary Schools. It says things like this:

Lots of girls & boys have written to this site asking about masturbation. Most people feel like touching their sex bits sometimes. Even little babies play with their sex bits, but as puberty starts the sexy feelings get stronger for girls & boys. Our sex bits have lots of nerve endings so when they are touched it can feel tingly & exciting. Touching your own sex bits to get sexy feelings is called ‘masturbation’.