Why do some schools outsource sex education these days?
Because the tories.
They decentralised education.
They are picking up the mess they created.
Labour had the curriculum and then created gov approved teaching materials- which were optional but as they were free, most used them.
Sex Ed often had some input from the LA health teams but otherwise it was also covered (under pshe). There were some well researched pshce schemes that were external but didn't really cocked sex Ed (for primary) and were more around self care, healthy living etc.
The tories expected schools to create their own materials which created the perfect storm of teachers leaving the profession to set up their own companies as well as charities and private businesses getting in on the act - especially in the realms of RSE due to the relationships aspect: LGB.
because teachers who've been around for a bit assume everything from charities and external providers is appropriate (as it was from the LEA in the past), and younger ones just trust the system, they have no reason to question it.