#wizard clothes

In the books wizards always wear robes and don't know how to match or even put on muggle clothes... yet Ron wears gym pants under his uniform robe.

And why exactly do they do not know muggle clothes? Rowling said (relatively) recently that many wizards attended muggle primary schools before being admited to Hogwarts. The Weasleys, for example, were homeschooled by Molly, but that's not the case for everyone, so all these wizards should have had learnt something about muggles during their years at primary school...

And still on the Why topic, I have read wizards got stuck in the fashion that was in fashion when the Statute of Secrecy was established (1689-1692), when they lost* contact with muggles (* but did they? all the kids going to primary schools?), except robes weren't really in fashion for men by 1689!

By 1689, men wore breeches and stockings under buttoned justaucorps (wich were knee long).

And, yeah, I get it. Harry Potter wasn't suppossed to be a big deal or to be taken seriously, so no one felt the necessity to do the proper research to be History compliant.

So I try to imagine wizards in actual late 17th century fashion ...but then SWM doesn't make sense! Because levicorpus just would't have exposed his underwear, which was kind of a decisive part of the event.

I have the purrfect spell for this!