I think that's cool having all of those non-humans in the school.
Idk if it's just me though but... I feel like """"non-humans"""" are really just variants of humans. Kind of like races like Asian or African or White or Latino. Because I mean irl legends start from 'Oh I saw this thing.' 'Oh you did? I did too!' Not 'Oh I saw this thing.' 'Oh I did too!' 'Yeah the moment I saw it I immediately knew of all it's origin and how it came into existence.' 'I know right because there's nothing like a legend that has a full backstory that definitely wasn't made up based on what we saw or anything.'
So I think you can think whatever you want to think about how 'non-humans' came to be and it'd still be right. I personally like believing they all originated from humans.