In Ender's Shadow Bean is informed that everyone in Battle School must eat all of their given food:
Your portions are scientifically calibrated to meet your dietary needs, and in the future you will finish every bit of what you are served."
However, in Ender's Game we learn that Ender "always" leaves food over after each meal:
Ender laughed. "I'll setup a system for you."
"Can I finish eating?"
"You never finish eating."
It was true. Ender's tray always had food on it after a meal. Ender looked at the plate and decided he was through. "Let's go then."
What makes Ender special? If anything, wouldn't the school be more on top of what Ender eats?