How the fuck did this ever come to pass.
So many things are outsourced now it's quite scary. In the past the LEAs had tight control over what was cascaded down to schools. They had advisors who were previously teachers who delivered lots of training. This still happens a bit, ironically mainly very key things such as safeguarding and ofsted stuff, but much less for wider curriculum things so any freebies are lapped up.
I'm also seeing young teachers leading on things they've not had a huge amount of training on. (Also not always great on their subject knowledge) It's encouraged as part of professional development and performance related pay; some of it though can be self taught, what they've come across etc. So for example, if they're putting together a scheme of work for PSHE and they find something pre made that gives a load of lesson plans they'll lap it up.
Things like the EA also can come top down from the LEA if the council has a wider agenda so obviously they'll look for materials to deliver this effectively. Esp regarding radicalisation and homophobia.
Under the previous national curriculum, the government produced schemes of work that delivered all the key objectives in the Nat curriculum. Slowly schools improved on these as they could be a bit dry, but were produced as not all teachers are experts in all subjects. They were always there as back up or to fall back on.
Most of this was ditched with the new curriculum a few years ago and many schools were left floundering. Adding in things like British values and diversity and the EA etc, teachers take what they can.
Schools love collecting badges too (helps tick off things for ofsted) so a badge for stonewall etc looks great.
IMHO its a free for all for who ever wants to shout the loudest. The SRE was supposedly being updated but I've not heard much and I think fucking Brexit has fucked up a lot of real thought in so many of these areas.
Safeguarding is the strongest thing we have and the area we must keep pointing out is being completely flounced.