I think it's a sad reflection on a 1st world country that this debate should even raise it's head. As someone who cooked school meals for over 20 years and was responsible for planning, purchasing and preparing nutritious meals for over 400 children everyday, they were always enjoyed by the children and deemed very good value. Everything was made from scratch, fresh vegetable, fish, meat was always served. I like to think that my contribution made up for the shortcomings of parents who didn't or couldn't cook. Very few children brought packed lunches and our lunches were far ahead of the times (aka Jamie Oliver).
Since then I have travelled overseas extensively and met parents who cook fresh vegetables and rice each morning so that their child would have a nutritous meal each day, they were poor but knew the importance of giving their children nutritious food. I'll stick my neck out and say that a parent who sends their child to school with crisps and biscuits for lunch is just plain lazy.