W.T.
Remember the good old days when we all took brown bags to school and the food was fine? :)
They've got great BPA free reusable lunch containers at Target and other places. Throw an ice pack in there and pack what you want. Unless it is put in the sun, everything will be fine. Think about picnics and potlucks when food is left out for a few hours and it is fine.
Cut up fruits and veggies. Yogurt, string cheese, boxed milks (soy or cows). My health food store sells litle packages of peanut butter (or almond or cashew if there are allergy concerns) that can be eaten quickly and pack good protein.
Sandwiches...stay away from mayo if you're worried. PB&J, cheese, etc.
Make up some pasta or bean salads that your child will eat and pack those all week. Homemade pizza? Veggie burger patties cut up in strips?
If you think you eat healthy and are concerned your child will want what others have, pack small portions of rice chips, soy chips, baked potato chips, etc.
Good luck!