[@Apollosarcher]

Haven't thought about that. Yeah... in theory it would be very interesting, but if one has to drop out...

Regarding they being "leashed" I don't think that it would be that much of a problem. The summon wouldn't be just a helper, but it would have its own wishes, its own personality. Maybe even go around the academy doing things for its own.
When its summoner needed it, it would be able to "summon" it by reciting the mantra (or something like that). Resulting in some pretty funny situations :lol