Ender's parents were indicated for smart children, and so the military monitored their children, looking for a specific blend of ruthlessness and compassion. Their first two children were on the two extremes, and so they were allowed to have a Third child. When speaking with Graff, Ender realizes that much of his life, including his conception, was planned:
"So my parents love me and don't love me?"
"They love you. The question is whether they want you here. Your presence in this house is a constant disruption. A source of tension. Do you understand?"
(Card, Ender's Game, Google Books)
Ender's parents love him as they love their other two children, but the planning behind his birth is too much for their family to handle. His older brother resents him and his status as Third makes him a target of bullies. In that sense, Ender's parents want him to succeed, but they are unsure that they can give him stability and nurturing with his innate problems. Instead, they make the difficult decision to allow him to attend Battle School; they know that he is needed to defend the human race against the Buggers, and they also know that this will give him a chance to be exceptional instead of merely good, as he might be if he stayed home.
Another emotion that Ender’s parents feel about Ender is proud. They are proud of the fact that their children have tested to be so high that the government has come to them and asked them to have a third child in a society that is only allowed to have two children. They are also proud when Ender is actually accepted into the program, although it does not seem to be that in the book at the time, but the bottom line is it would be better for them to be proud of a child who is away serving in battle school, rather than ashamed to have a third child at home who was not considered “good enough” to be of a help to the military.