In DDs small village school the problem will be lack of space.
The children who have a school dinner cram into one classroom, which is then pretty disgusting for the rest of the day (spilled peas and gravy on the carpet, smell of food). The packed lunch children usually eat outside unless there is a gale or a blizzard, which means they get more fresh air and their classroom doesn't stink afterwards.
The food is brought in ready-cooked because there are no cooking facilities - so I'm not sure just how healthy it is.
So on the whole, yet another idea designed to win votes but not thought through at all.