My DS's preschool had a setup like KJP is describing. But, in his 1st grade class now, they do not have a snack break in the morning - instead they eat lunch early at 11:30 AM. I load up DS with breakfast and fruit and water and send him on his way each morning. His behavior changes drastically when he is hungry. When I pick him up from school, there is a small packed snack in the backseat. My DS has never once asked for food in his life - just does not feel hunger. He is intense in playing and never stops to consider whether he is tired or hungry. I have learnt to anticipate hunger and constantly give him snacks before the behavior deteriorates. I also carry snack bags every time we set out for extracurriculars or small trips so that he is constantly fed. The snacks I carry are: cheese sticks, carrots, cucumbers, craisins, dates, graham crackers, cheese crackers, grapes, strawberries, bananas, apple slices with cream cheese, granola bars, fruit chips, milk cartons, yogurt squeeze tubes.