Definitely not. Of course, this is the reason why Ender is so special and why he has been selected as the possible future saviour of mankind. Note how he acts in the fight with Stilson. He shows an understanding of human psychology and a willingness to act on his keen intelligence that is above and beyond nearly all six-year-olds. Let us examine his thinking:
Ender knew the unspoken rules of manly warfare, even though he was only six. It was forbidden to strike at an opponent who lay helpless on the ground; only an animal would do that.
And that is of course precisely what Ender does. He cooly and calculatedly kicks Stilson's supine body hard, twice, in his groin and ribs. Of course, he knows that he has to hurt Stilson so badly that nobody else would want to bother him to ensure his survival. This is definitely not the behaviour of your average six-year-old.