Literally no one is saying that men and women can change their biological sex. Zero. It’s not happening anywhere. Either you know this and are making an argument in bad faith or you actually believe this and are making an argument from ignorance. Either way, your point isn’t valid.In your opinion it's not real (my opinion too). However, our opinions are meaningless and you can not scientifically disprove the existence of a god. We could easily be wrong and there could be a God.
On the flip side, we can say with scientific certainty, that men cannot birth children. We can also say with scientific certainty that men cannot switch their sex from male to female and vice versa.
You conflate opinion with fact.
But, if you want to go down that road… you can’t scientifically disprove that a biological man can switch their biological sex and become a biological woman. It happens in other species. What you mean to say is that there is no evidence that a biological man can become a biological woman, just like there is no evidence that any god exists. So if it’s acceptable to tech religion despite there being no evidence just because it cannot be scientifically disproven, can’t we really just teach anything?