I think the c ollars should totally be to keep them from saying what they're hiding. But I think that what they're hiding should combine the good and the bad. Like that they all have powers because they committed a ritual sacrifice of another student to a demon in order to become empowered. Or something like that. ..
Hmmm, possibly... I think the main question is how magic-heavy the world is, and if there'd be other races aside from humans really. But possibly interested depending on how things turn out I guess.
Here, here! What Rin said. Magic? Elves? Dwarves? Orcs?