Sexual health charities Brook and the Family Planning Association are calling for sex education for kids as young as four so as to reduce teen pregnancies.
The charities said children should be taught about sex so that they are aware of things like abortions and sexually transmitted infections when adolescents.
"If we get high-quality sex and relationships education in every primary and secondary school across the UK all the evidence shows teenage pregnancy rates will continue to fall and will improve young people's sexual health," said Brook chief executive, Simon Blake.
"This is not about teaching four-year-olds how to have sex ... it's like maths - at primary school children learn the basics so that they can understand more and more complex concepts at a later stage," said Julie Bentley, the Family Planning Association chief executive.
Yesterday the Department for Children, Schools and Families issued new draft guidance for schools. The Sex Education Forum has called for sex education to be made mandatory in schools.