I'm a high school teacher and we have finally gone over to a healthy canteen provider (after years of the most expensive, disgusting food you could ever come across) - they have tubs of salad, yoghurt, sandwiches, sushi rolls, fruit etc that all have the green light, then there's amber choices (ie, only eat occasionally) like toasted Turkish bread rolls with REALLY yummy fillings, curries and rice etc. It has made a huge difference - staff eat on site, kids no longer skip class to go to Maccas etc. It is cheap, fresh and tasty.