After the Third Formic war was won by Ender Wiggin, the alien threat to Earth was over. The terraformed Formic worlds were open to settlement by humans and the International Fleet became the arm of the Ministry of Colonization, run by Hirum Graff. MinCol now runs Fleet School on the old Battle School station, and still recruits very smart kids to train as leaders of colony ships and colonies.
Dabeet Ochoa is a very smart kid. Top of his class in every school. But he doesn't think he has a chance at Fleet School, because he has no connections to the Fleet. That he knows of. At least until the day that Colonel Graff arrives at his school for an interview.