The first one features an "elder dragon" masquerading as the headmistress of a middle school where banished bad guys from a magical realm become the teachers. Imagine the horror: a life sentence to teach middle school? That would be enough to make any villain re-think a life of conquest! The MC is a young dragon slayer who doesn't get to slay any dragons, but is caught in 7th grade. Did I mentioned the banished bad guys are the teachers? Sound like your middle school? Mine , too.
The second one is a cute, quick read, and features a female dragon who's a bit confused on the whole "ownership" concept.
The third features a nutty professor-type who meets and finally is forced to acknowledge he trained his arch nemesis.
The fourth features a MC trying to thwart a dragon-slaying quest, travel by dragon fire ball and battling giant, indestructible robots.