School meals only account for one meal a day, they are not much of a problem even if they sometimes have odd combinations. My kids were amused and baffled by a vegetable curry being served with mashed potatoes, baked beans, cabbage and sweetcorn. To be fair the other option was pork chops and there are only a handful of vegetarian children in a school of 30 kids, so no harm they still enjoyed it.
We are vegan at home, our school can't cater for vegans which is fine. We have many allergy considerations at school so I don't dare send a packed lunch as we use a lot of nuts at home and I'm worried about cross contamination.
I think obesity is linked to too many thinks to have a sole cause for each person. Genetics, excercises, understanding of ingredients, portion size. After becoming very ill a few years ago I taught myself about food, ingredients, nutrition, labelling the whole shebang. I became vegan, I've been coeliac since I was 16 so I've never really eaten a lot of bread or cake. I think right now we are very healthy and we all feel good for it, my husband is vegan, pescetarian at work and the kids are vegetarian. We eat so much Indian, Thai, Greek and African dishes as they veganise very easily. We also walk everywhere as I don't drive.
I think education is key I love Michael Pollans advice he advocates eating products with as few ingredients as possible and food great grandmas would recognise and Michael Moseley who advices we move more especially before we eat. Easy simple advice.
Main thing is though not to blame people, some folk just need a bit of help.