Because the adults in the book manipulate the children, we spent quite a bit of time discussing whether or not this is justifiable. And you know what? The students claimed that it was. The adults, according to the students, are justified in their manipulation because in the end, they are simply trying to build an adequate general to fight off the buggers.
We also discussed how far Ender goes to protect himself. In two different situations within the book, Ender fights another boy, and fights him to the point where he knows the boy won't come after him again. This brought up issues of bullying and many of the students at our little charter school have been bullied. The students claim that again, Ender did the right and justifiable action; otherwise he would have been severely hurt himself. I have to admit, I was on the other side of this one and didn't agree, but I was voted down.
Lastly, we discussed the ultimate message of the book. Is it okay to destroy another species (or culture) simply because we are unable to communicate with them, and why do humans seem to react in this way so quickly and often? We sited many examples from history where wars were started due to lack of communication, and where a culture was decimated because another culture didn't understand them. This is a profound and honest look at who we are as human beings and it makes us examine our priorities and aggressive techniques.
This is a great book to discuss with adolescents. So many of the issues relate to their lives in some way and many of the themes contain multiple points of view. Thanks, Orson Scott Card, for developing a book that teens relate to on a personal level, but also brings them to a level of thinking that goes beyond black and white.