It won't happen to us. All the professors tried like mad to help Capper and he only ever cared about Arithmancy. We're not pillocks, we'll take help where we need it.

And once we're done with school, loyalty counts a lot more than marks. It's not just half-bloods who can get sent to the camps -- people like the Weasley Twins will need to watch their step once they get out into the real world.