Parents are the ones who see their child developing and who are responsible for ensuring they know what they need to know. My dd was a very well developed 10 year old and although they had a little talk in Y5 it was me that noticed the development and who provided additional information and support and took her to Boots to chose some Sanitory towels and a little make up bag for them, etc.. It was me who supported her and loved her and had to go to see the head because there were no sanni bins and little privacy in the school loos.
Just like it was me and DH who have had chats with the DS about his spots, girls, snogging, etc.. Just it's the parents' responsibility to tell them to be safe to mix sensibly and chose their friends with care; to underpin it all with a note about long term meaningful relationships, about caring for others, about how lives get wrecked by unwanted pregnancy, etc., and how it is always better to plan ahead.
I think our DC have had enough sex and relationships education at school but that it is up to us as parents to build on it and to provide advice and common sense to make sure they are aware of their developing sexuality and have the values that make a successful caring life drilled in too.
Let their teachers focus on the basics that I can't teach; literacy, maths, french, physics, etc., and let parents focus on sending in well balanced, well behaved children receptive to the learning they offer.