The BBC Bitesize video linked to in this thread is not the one parents are objecting to.
"After Mr Doherty complained to the BBC, the video was removed from their website."
That one did show erection and ejaculation.
Puberty and sex education does need to be taught in schools in an age appropriate way - how and why the body changes, menstruation, how babies are made and born, consent and how to stay safe.
I don't think any child needs to be taught the A to Z of sex acts in all the combinations possible, certainly not before they are 13.