Hey Beth, You should try packing your lunch. Thier are a lot of things you can bring with you that won't go bad and are certainly better than what the school has to offer.
Some things you could try:
Peanut butter sandwiches
Pasta or rice salad (with a little salad dressing instead of mayo).
Chicken salad with nuts and apples (little or no mayo)
Grilled Vegetable sandwiches
peanuts and raisins for snack
granola bars