Isn't Hogwarts supposed to be like a high school/college anyway? From the books, it sounds like the classes are not at elementary school level once they finish the first year or two. You'd probably have to be pretty intelligent to get a passing grade in one of Snape's classes. I was always terrible at chemistry myself.

I believe there's a hero in all of us that keeps us honest, gives us strength, makes us noble, and finally allows us to die with pride, even though sometimes we have to be steady and give up the thing we want the most. Even our dreams. -- Aunt May, Spider-Man 2