Our school's healthy eating policy has a blanket ban on nuts (allergies throughout school) but none on eggs (serious allergy sufferer in DD's class).
In general, it is about healthy eating. Preferably brown bread for sambos, ideas for non-sambo snacks sent home occasionally (like wraps, pasta salad, carrot sticks/breadsticks and humus or salsa in a tub etc). Plain biscuit or home baking is allowed, but no crisps, sweets or chocolate in general. We allow a treat on a Friday and school has not said a word about it (like maybe a choc covered rice cake - DD likes them - or a caramel wafer biscuit).
There is a lot of emphasis on fruit and veggies - the whole school did the "Food Dudes" programme this year again, they grow veg in the school garden and it's part of the active healthy eating promotion they do.
No fizzy drinks, but water or squash or fruit juice is fine.
Cheese is great. Yoghurts are ok, but they prefer not to have them in the junior classes (junior and senior infants, aged 4-6ish) as the teachers end up having to open 27 pots for the kids and no one has time to finish them then so big messes!! They recommend not sending milk, purely because it can go off so quickly in the heat.
DD has brought a wide range of things. We've never had anything rejected, dumped or sent home by school. (She, on the other hand, can be fussy and reject half the lunchbox!!).
Things like chunks of cheese (good days) or cheese dipper/dunkers (less good days) are relative staples. Sometimes a sambo, other times crackers with a tub of ham or chicken pieces, or grated cheese, or tuna/sweetcorn mix to put on the crackers. She loves carrot sticks and salsa. She loves whole tomatoes to eat as a fruit. She'd have apples, bananas, pears, grapes, raisins or strawberries as other fruit. Occasionally she'll have yoghurts (she is able to open them herself) - either a M*ller corners one (bad mammy days) or the tubs of fruit puree for babies (like a pot of yoghurt only it's pure fruit - she really loves those and calls them her yoghurts). She'd usually have a sports bottle of squash to drink, or plain water, occasionally she'll have an Innocent smoothie.