DD1's school has Brain food, snack and lunch. The encourage nude food.

Brain food (as it is eaten in the class room)- is either cut up fruit, veggie sticks or cheese (no crackers). On Fridays the fruit is provided for free and there is a share platter cut up
Snack: Sometimes muesli bar, choc banana muffin, pikelets, pretty much whatever I can find in the house (I bake batches of muffins and freeze them)
Lunch: Sandwiches and a yoghurt (same a Onyx, make a weeks worth at once and freeze, so important with lunch not being till 1pm). Occasionally will put in leftover dinner if it is suitable (eg sausage and salad)

Also use freezer blocks, even though some of the food is frozen.