Ender was the main focus in the book but you also witnessed others being played. His school mates were put in a place of complete chaos and daily living was unpredictable. Even though Ender was the end all be all student they all still needed to be trained just in case. In case he failed to do what he was trained to do. Two boys died in this story because the teachers pushed him into defending himself to the point that those boys and others would just leave him alone. Then Bean came into the picture and Ender had someone to make into the perfect solider. Even though Ender couldn’t stand being treated and humiliated like he was he started in on Bean. It became an ugly cycle that continued on until Ender realized that he was doing wrong. Graff had several logs in the book where he regrets what he has done to this boy and wishes that he could take it back really undo what he has done. Then he comes back to what he knows as his reality and continues on with the constant manipulation.

Valentine was also used by Peter in a less aggressive manner. He wants to take over the world at some point and control everything around him. So he persuades her to start writing and contributing to his plan of domination. Well thought out he does continue on to become the leader of the world. Even after he has power he tries to convince Ender to come back and be a part of his legends.

What we have to think about now is whether or not we ourselves would put children through this brutal training in hopes of one day saving the world. I personally do not understand why we needed young minds in order to make their plans work. Why not have people that freely take on the responsibility of saving the world. Someone who has had the chance to become the person that they themselves want to be.

In their moral theories, the ancient philosophers depended on several important notions. These include virtue and the virtues, happiness (eudaimonia), and the soul. We can begin with virtue (http://plato.stanford.edu/entries/ethics-ancient/). In the ancient world, courage, moderation, and justice were prime species of moral virtue. A virtue is a settled disposition to act in a certain way; justice, for instance, is the settled disposition to act, let's say, so that each one receives their due. This settled disposition includes a practical knowledge about how to bring it about, in each situation, that each receives their due. It also includes a strong positive attitude toward bringing it about that each receives their due. Just people, then, are not ones who occasionally act justly, or even who regularly act justly but do so out of some other motive; rather they are people who reliably act that way because they place a positive, high intrinsic value on rendering to each their due and they are good at it. Courage is a settled disposition that allows one to act reliably to pursue right ends in fearful situations, because one values so acting intrinsically. Moderation is the virtue that deals similarly with one's appetites and emotions. (http://plato.stanford.edu/entries/ethics-ancient/)

Now I believe that Ender himself was one of only a few in this book that had any ethics or virtues to lean on to keep him who he needed to be. If you have a chance read the book it kept me into in the entire time.

References:
Card, Orson Scott. Ender’s Game. New York: Tor Books, 1991
http://plato.stanford.edu/entries/ethics-ancient/