Ender's Game - like

This is a very good book. A six-year-old is selected to attend this super advanced military training school, because the world is still always in preparation to fight again against the alien "buggers" that nearly destroyed them 70 years ago.

But he's not an ordinary six-year-old. His older brother was selected to try out first, but was too vicious. Then they asked his parents for a girl - just as advanced, but hopefully less violent. But then she was too uncompetitive. In this world, only two children are the norm, but they (the military) were desperate, and hoped for the third child to be a mix of his two older siblings. And so Andrew (Ender) was born.

Read the book before they make a movie out of it and ruin the story.