I read these books when I was kid (early 1980's) and think they were published in late 60's, early 70's or possibly later.
The premise was of a training group for teens to train them to be some kind of space warriors or peacekeepers. There were cool weapons, tactics, training, tech, etc.
There's some kind of treachery and the whole school/academy is wiped out, except one pupil (possibly one or two others?) who escapes in a ship and spends the remainder of the book series fighting the forces that killed all the other students.