Ethnicity wise we also don't know what the rest of the student population were as it's just not mentioned. The ones we know about these were the characters who were specifically mentioned
I always assumed that Hermione was mixed-race. So I found Emma Watson's casting very jarring and wrong. I also assumed, because a few non/WASP names and characters were given, that there must have been more and that the school body was not overwhelmingly white. To list lots of non-WASP characters would have been sickly virtue-signalling. After all, Neville (just for example) is not described as white IIRC, just that he has jug ears. He could have been black, or Korean, or anything. So non-WASP readers could well have imagined the characters in their own images. And ethnically diverse individuals in the UK do not always have 'forrin' names, anyway.
The film makers should have cast so much more diversely. What a missed opportunity.