Starkadder, your dh's experience is quite unusual & outdated.
10 years ago PSHCE was routinely the responsibility of form tutors at my school - I've taught it quite competently, I think, but these days it's more usually under the RE 'umbrella' - called something like 'Integrated Studies' or 'Ethics'.
Agree with earlier posters that the 'mechanics' are taught as part of Science, so if you'd prefer your dc not to know what goes where & the potential consequences, withdrawing them from Sex Ed will not keep them adequately ignorant.
What depresses me is the presumption by some posters that teachers are routinely foisting their stereotypically libertine ideas on delicate innocents. No. It just doesn't work like that.
For a start, we are professionals. Keeping one's personal opinion separate from one's teaching is not a skill any teacher is unfamiliar with. If someone told me 'my mum thinks that...' I wouldn't dream of telling them their mum was 'wrong'.
If asked what I thought, I'd be honest, never prescriptive. ('Well, I think...., but what's more important is what you think')
& where sexual 'permissiveness' is concerned - & it seems to be the main area that parents get panicky, sorry, concerned, about - honestly, you'll find very few teachers gaily advocating unfettered & feckless teenage shagging. If nothing else, it plays merry hell with those vital GCSE results...