Supernova

Supernova continues where Light Years left off. It is filled with all the "galactic boarding school" tropes. The kids fall in love with each other. They fight. There are battles over a girl. There is a giant conflict where the adults are messing things up and only the kids can make things right. Even though it is set in a distant world, the people share the same liberal values of our society.

The book is not long, but it does suffer from too many characters. Some characters seem to play an important role, but then just disappear. (It is not clear what happened to the "bully") Others seem to have no real purpose in the plot. (There is a regular interlude with two boys in love - but they don't seem to do much for the story other than fall in love.) The main characters do stupid rash things, but every thing works out due to some dumb luck. The only real loser is an authority figure who was trying to prolong the war to benefit military contractors.

Light Years

The story begins on a mining planet where the unfiltered air will kill you after a few minutes. The wealthy live comfortable, but miner deaths are a frequent occurrence. A black market runner discovers that his older brother dies right before he was to go to fleet school off planet. The boy ends up taking his identity.

The civilization is at war with other groups. Things are so desperate that they are willing to take in people from "Edge" worlds into the military. This sets up your typical youth boarding school scenario. There are the rich that oppress the poor. The fashionable meet the functional and plenty of romances of various gender relationships break out along with requisite conflicts.

There are also plenty of nefarious activities. The "identity thief" bets against himself and uses the money to pay somebody to swap out his medical records so he won't get caught. One girl is a spy for the enemy race. The biggest scorn is laid on the boy who is a bigot towards the lower class people. 

There are the typical training and social dramas, then a real world invasion at the end. We also learn a bit about the enemy and that the conflict is not quite so black and white. There are plenty of open threads left for a sequel.