I usually bring yogurt, bananas, apples and oranges for snacks. since your school is peanut free, try some cheese with the apples. A lot of time this might wind up being lunch. In warmer weather, I get the bags of salad and bring some cut up meat and have that for lunch--sometimes I may have a roll with it. Another way to have salad is to fix up your salad with you dressing and the wrap it up with a pita bread. It's filling and healthy at the same time.
a lot of times I will just make a little extra for dinner and make up lunch from the leftovers.