Since my DDs thankfully just missed all this (age 22,24) forgive me if I'm not fully up with legislation etc.
But my understanding is that external providers coming in is a fairly recent (? last five years) occurrence, I think I read somewhere about changes in the law that allowed it.
While there were people like Dr Christian Jessen waxing lyrical about "experts" giving high quality education (and also advocating for porn to be used in a teaching scenario "so they understand what it's about" or some crap like that) I think many of us (Me) pretty much had no idea what the implications were. In hindsight it was so obvious that this would attract organisations with different standards to what most parents would have expected (putting it mildly).
We really need to get these organisations out of schools. And the curriculum imo needs to be tightly controlled and of course available for parents to see.