I don’t disagree that the classmate felt shamed, since she cried I would assume she did. People who aren’t prepared for debate often feel shame when their ideas are exposed as ridiculous. 13 year olds are not going to have the best skills for challenging gently, nor the best for accepting that their ideas aren’t accepted by everyone. That’s a really tricky discussion for a teacher to lead well and one that, I would think, was inappropriate at that age without a lot of prep work.
That doesn’t make what the kids were doing “just mucking about” as you claim. They are being introduced to ideas that they find unbelievable - which isn’t surprising, since vast majority of people find the idea of being cat gender unbelievable - they challenged that. That’s not “just mucking around”, it’s engaging in learning. Questioning what you don’t understand is essential to gaining understanding They may not have the best skills to do so well, and a good teacher would hopefully be able to help the whole class develop the sort of discursive and critical thinking skills necessary to do it respectfully. This teacher didn’t attempt to do so. Given her own appalling grasp of the issues she was clearly ill prepared on the specific subject matter, but that doesn’t mean she shouldn’t have been able to model the skills she wanted to see from the kids instead of trying to shame them (which was spectacularly unsuccessful given she couldn’t string a coherent sentence about the ideas together) and threatening them about their place in the school.
*All this assumes there was a girl who identified as a cat and cried in class - which, if we are to believe the guardian, may not have been the case at all, in which case we are simply talking about discussing the idea of identity theory, not about kids who shamed another child.