My daughters at secondary school now so she uses the canteen, but when she was at primary school I was very particular. She got sandwiches (with healthy contents, none of that billy bear crap!), fruit, a drink and occasionally a packet of crisps or a biscuit. Young children need good nutrition to help them grow and learn and those people who cant be bothered to deal with their kids food issues and just feed them crap because its the easy option need to review their parenting skills frankly. Sorry if this offends but I feel quite strongly about this issue, it's no wonder so many of our kids are suffering with obesity and diet related health problems.
I'm actually torn over this issue of schools telling parents what they can and cannot put in a lunchbox. I believe that a balanced diet should be just that - balanced. This means that a chocolate biscuit is ok provided its every now and again. Now I can understand why schools have implemented these rules when you look at the rubbish some people send their kids with, but I remember being told I couldnt put a penguin biscuit in my daughters lunchbox, even though it was an occasional treat. My two main issues with this are that firstly, you shouldnt encourage kids to have food hang-ups, that's a sure way to breed a yo-yo dieter. If you give kids the idea that eating chocolate is a bad thing they will develop a guilt complex about it and I dont think thats a healthy thing to do. My second problem with schools is that they ought to look at their own menus before telling parents what to do! If your kiddie has a school meal, they get frozen pre formed crap thats been coated in breadcrumbs and deep fried, and for pudding they get a daily sugar fix, usually some sort of sponge and custard, that's hardly healthy!