People seem to be variously wibbling and incandescing about the possibility that the students in the next HP film will be seen not wearing uniform.
When I was at boarding school we had uniform, except for the Sixth and Upper Sixth, but we weren't expected to wear it except during the day. In the evenings, on half days and weekends we wore Muggleordinary clothing.
I can see a case for the Wizard-born's version of 'ordinary clothing' being robes (but I'd be prepared to argue perhaps only the most hidebound of Slytherins would want to wear robes all the time), but surely the Muggle-born would have spent their first eleven years wearing jeans, trainers and hoodies, just like the rest of us, and even though at Hogwarts still feel most comfortable in them?