"I mean the whole series of books is little more than an upper class English public school fantasy where (almost exclusively) white elites preside over the 'lesser' races and classes."
We actually don't know about the classes of the vast majority of students at Hogwarts. The ones we do know about it's implied that the main characters are middle class (Hermione and Harry) and maybe working class (Ron - although he is merely poor).
The books were about blood status though. Again we don't know the blood status of the
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:
the Patil sisters (probably British Asian - of Hindu religion) Harry and Ron go on a date with.
Ginny goes out with Dean Thomas. Angelina Johnson - quidditch captain of Gryffindor and dates a Weasley (and marries another Weasley).
Cho Chang who Harry fancies and dates.
Kingsley who is the Order.
Blaise in Slytherin.
Lee Jordan is implied to be black because of his hair.
The point of this post was to say that you're making an assumption based on what you thought. As a person of colour, I was thrilled to see so many kids who were like me. And the most important bit: These books were written in the late 1990s/early 2000s and it was rare to see characters from different ethnicities in children's books so JK Rowling did a brilliant job of representing us.