Associate
Both of my kids have been through this program. Just to make it clear, it's not sex education in the way hysterical Daily Mail headlines would have you believe - it's call SRE (Sex and Relationship Education), and starts at reception then carries on all the way through secondary.
This.
As well as having kids at school I'm a governor at a school nearby - not sure the precise details of the curriculum at the schools in the news, but the one my kids have and at the other school is pretty good. Starts simple at reception (my son's class has a girl with two dads for example, so they talk about family units) and then by year 6 (kids are age 10-11) they are getting in to puberty, a bit about relationships, the mechanics of sex and starting to point out some of the complexities of gender. Seems very sensible to me.