My 4y/o brings a box to school with 1 piece of fruit (some bring a cookie/oat bar or something but the school encourages fruit) and a bottle of water which is eaten around 10:15 I believe. I think this is only for young children.
By the way, if a kid forgets his or her fruit they make it point to share, I like that policy. Also I hear from colleagues more and more schools are switching to water only to battle weight increase in children, although this leads to some discussion :)
Edit: see below, the Netherlands is waking up I guess :)
Some schools (kindergarten, primary and secondary) do offer the possibility to buy lunches. But those are quite expensive (more than $2, for 4y olds in my kids' previous school) and not very healthy, since at that scale, cost of food matters a lot.
On the other hand, there's no lunch bill, as kids have to purchase the lunch tickets upfront. I'm actually not sure what happens if the kid says he has no money; I'm pretty sure my classmates would be too embarrassed to do so. The few times one of them didn't have money, we either knew beforehand (and pooled money ourselves) or the kid just went hungry.