Ender's Game

To develop a secure defense against a hostile alien race's next attack, the government breeds child geniuses and trains them as soldiers. The brilliant young boy, Andrew Ender Wiggin, lives with his kind but distant parents and his sister, who he loves more than anyone else.

Peter was also drafted to the Battle School for rigorous military training but didn't cut. However, Andrew was a school leader and respected in the Battle Room, where he played mock battles in zero gravity.

But growing up in an artificial community of young soldiers, Ender suffers greatly from isolation, rivalry from his peers, and pressure from the adult teachers.