Apologies, I was wrong. This is from the BBC, wrt England:
England
Under the Learning and Skills Act 2000 in England, a school's SRE policy must be available for parents to inspect. Primary schools are not required to teach SRE other than those elements that fall under the Science curriculum. However, they are required to either have a policy on SRE outlining details of their programme or explaining their reasons for not giving one. Primary school children can expect to be taught the names and functions of external body parts, and be informed about puberty before it begins.
In England, the sex education elements of the Science area of the National Curriculum are compulsory for all pupils of primary and secondary school age (7-16). They include biological aspects of human reproduction, anatomy, puberty, uses of hormones to control fertility and how viruses can affect human health.
At a minimum, information about sexually transmitted infection (STIs) and HIV/AIDS will be taught.
Other elements of sex and relationships education are taught as part of a Personal, Social and Health and Economic Education (PHSEE) programme, which may also include subjects such as citizenship and drug and alcohol awareness. However, SRE is not a compulsory part of the national curriculum.
In secondary education, the school governers will be able to provide an up-to-date policy describing the content that your child is taught.