Probably a lot. I suspect that the school receives money from the state for each school lunch provided. Every bag lunch, is money lost.
This would be like the FTE (Full Time Equavalent) which determines how much money the school gets from the state, except for food not seats in chairs.
I suspect you are right! You know, I don't need a job, but I would offer to work for free if the govt were hiring someone to look into waste, skimming and fraud in govt-funded program like that. But I don't think they WANT to look into it.