Page 91 - Enders_Game_Full_Book

Fortunately, they knew as little about nullo fighting as he did, and the few that tried to punch him found that throwing a punch was pretty ineffective when their bodies moved backward just as quickly as their fists moved forward. But there were some in the group who had bone-breaking on their minds, as Ender quickly saw. He didn't plan to be there for it, though.
He caught one of the punchers by the arm and threw him as hard as he could. It hurled Ender out of the way of the rest of the first onslaught, though he still wasn't getting any closer to the door. "Stay there!" he shouted at his friends, who obviously were forming up to come and rescue him. "Just stay there!"
Someone caught Ender by the foot. The tight grip gave Ender some leverage; he was able to stamp firmly on the other boy's ear and shoulder, making him cry out and let go. If the boy had let go just as Ender kicked downward, it would have hurt much less and allowed Ender to use the maneuver as a launch. Instead, the boy had hung on too well; his ear was torn and scattering blood in the air, and Ender was drifting even more slowly.
I'm doing it again, thought Ender. I'm hurting people again, just to save myself. Why don't they leave me alone, so I don't have to hurt them?
Three more boys were converging on him now, and this time they were acting together. Still, they had to grab him before they could hurt him. Ender positioned himself quickly so that two of them would take his feet, leaving his hands free to deal with the third.
Sure enough, they took the bait. Ender grasped the shoulders of the third boy's shirt and pulled him up sharply, butting him in the face with his helmet. Again a scream and a shower of blood. The two boys who had his legs were wrenching at them, twisting him. Ender threw the boy with the bleeding nose at one of them; they entangled, and Ender's leg came free. It was a simple matter then to use the other boy's hold for leverage to kick him firmly in the groin, then shove off him in the direction of the door. He didn't get that good a launch, so that his speed was nothing special, but it didn't matter. No one was following him.
He got to his friends at the door. They caught him and handed him along to the door. They were laughing and slapping him playfully. "You bad!" they said. "You scary! You flame!"
"Practice is over for the day," Ender said.
"They'll be back tomorrow," said Shen.
"Won't do them any good," said Ender. "If they come without suits, we'll do this again. If they come with suits, we can flash them."
"Besides," said Alai, "the teachers won't let it happen."