It has nothing to do with eating. It's just when they get counted for roll and get counted for their school funds. All the school admin cares about is that money.
I know that (used to work at a school), but was trying to be a wiseguy and say most of us used to call "nutrition time" recess. Got corrected that it was lunch time, and was pointing out that 10:00 was a bit early for lunch. Guess when I have to explain it all, it's not very funny!! ;>)