$10 a week is reasonable, but may not buy lunch the whole week - most school canteens charge close to retail prices for things like snacks, but I know the local high school here does a $6 sweet chilli chicken wrap which is cheaper than cafes. What about a bento box style lunch? Containers with salad and finger foods that she can either eat all or some of and not spoil? My girls like to take carrot/celery/capsicum sticks to have with cheese and jatz and if they don't eat it all, I can use it the next day because it keeps pretty well.