Wow, this ancient thread of mine gets resurrected again and again...apparently this is a hot topic for a number of families.
I figured I might as well write a little update: while we're not slaves to the clock anymore, this issue has never really gone away.
In some ways things have gotten easier (mealtimes shifting an hour back or forth do not make that much difference anymore, so more flexibility during the day, and he's eating a good variety of foods) but also harder, as DS1 is now more responsible for his own food intake.
In preschool, the teachers would make sure that everyone had their snack by 11 am, in 1st grade, not so much. And on his own, DS1 is just way too distracted to get a meal inside himself without prompting.
So far, school's half days till 12.30, sometimes afternoon care till 13.15, but he has lunch at home everyday as i am currently on maternity leave and DH's schedule (teacher in a neighbouring school and on 70%) works out so he can give him a lift. It will make enrolling him in afternoon care, as planned at some point, difficult though, unless i can get someone to monitor his food intake - it's in their best interest!
Feeling more relaxed about this at home these days, I often forget about the snack in the afternoon, so if I haven't thought of getting him to eat something by 5 pm, he'll go berserk about trivial frustrations. (He is still unable to realize he is hungry and ask for food - DD, almost 4 years younger, will say "I need something to eat!", DS1 will just explode). I have explained the problem to him, the scientific basis and how it runs in the family and that the only means for him to be able to calm down is to eat regular meals, but he is still unable to monitor his intake or even to just eat once I tell him that he has to in order to calm down. He'll just scream and refuse and I have to yell at him even louder to make him. It's exhausting, but I guess it's my fault - he does not feel hunger himself anymore than I can feel it for him, but is just not old enough to monitor his own meal schedule.
DH has been yelling bloody murder at finding his uneaten snack in his schoolbag again and again, and I have asked his teacher to keep an eye on it. Not that I am very sanguine about this with 24 kids in the classroom, but at least if he ever has an explosion in school (so far, he controls himself very well) I can shift some of the blame!