School food has improved: there is now usually a choice and schools are becoming very conscious of the need for healthy eating (although the pupils still want chips). Most schools will cater for children who are vegetarian or those with special diets. Several schools have food committees. Some day schools allow packed lunches.
Food is, of course, especially important for boarders, so check out what other food is available (tuck shops etc). Senior boarders may have some cooking facilities or access to takeaways.