the business about 'three sexes' was MAYBE acceptable from a PSHE teacher, maybe, though it was worrying. if it came from a science teacher then heads really need to roll
But @puffyisgood why should young pre teen children be expected to sit in one lesson (PSHE) and accept what they are told (there are 3 sexes, male, female and both) and then move along the corridor to their science lesson and sit a test on mammalian reproduction and not mention the 3 sexes.
Why should children, in their educational establishments, have to navigate this? On pain of being told to leave if they raise queries or let on that they're a bit uncertain as to what to believe.
We do this with NO other subject. Indeed, cross-curricular learning is a very popular thing - ie a forest school session where you collect different leaves, divide them according to their characteristics, count their groupings etc, lay them out in a mandala shape can cover science, maths, mental well-being, art & design.... A cookery session can cover science, fair trade, business skills, motor skills, maths etc
We don't constantly tell children to leave what they think they know at the door for each separate learning. Any educational professional will have heard more about scaffolding learning, sorial and helical structured curriculum etc than they've had hot dinners.
If adults do introduce controversial, unfounded or unevidenced materials/subjects or discuss matters of faith and belief, then EVERYTHING should be couched in terms of "some people believe...."