Similar to you OP, I work in a school where over 60% of the kids are in receipt of free school meals. Many of the kids reality is heartbreaking and they absolutely would not have a microwave or probably a functioning cooker. Many live in temporary accommodation or in houses of multiple occupancy where they have a kettle and possible a toaster.
For a 16 year old boy the school lunch is very small but for some this will be the only food they are given that day, alongside a free protein bar for breakfast. Some will have scant food at the weekends. Very few are overweight. Calories in any form are needed, unfortunately nutrition has to come second.
The kids are also susceptible to the same marketing as other kids and any more nutritious or imaginative food will be left unused as they don't know how to eat it or don't like it as its not familiar.
We supply this: Pot noodles, super noodles, brioche/croissant packages, cup a soups, tinned ravioli etc if they have access to a hob or microwave, hot choc powder, biscuits, flavoured rice cakes, crackers, crisps, popcorn, small cereal boxes, uht milk, jerky/cured meat, tinned meat/ fish, malt loaf, sandwich spreads and bread. Dried fruit and nuts, hotdogs.
Nobody takes the piss.