What does it first seem Graff has arrived to do

At first, it seems as thought Colonel Graff has arrived at the Wiggin household to confront Ender about his previous encounter with Stilson, possibly taking him away to a place where he would be of no danger to anyone else. When Ender tell's the Colonel why he kept striking Stilson long after he had hit the ground, it was clear that all Graff wanted, was to see if Ender was adequate for Battle School. He'd already seen his physical strength, but was yet to find out his logical reasoning.