Black Magic Academy by Emily Martha Sorensen

Mildred doesn't like black magic. But her mother was once valedictorian of Black Magic Academy, so her aunts insist she needs to follow in her footsteps and become one too.
Mildred doesn't want to be part of the popular crowd. Nor does she care about her "death-enemy." And she certainly has no interest in murderous spells. But if the teachers catch on that she's actually a good witch . . . well, they don't react well to that kind of ignominy.
What's the only good witch in a school of wicked witches to do?