A tangentially related story: Seattle's public school teachers are threatening to strike. One of their demands (in addition to pay and such) is that children get at least 30 minutes of recess per day for elementary school students.
If anything, without more evidence, we might as well chalk-up the pre-school teachers' threats to strike as being self-motivated. I.e. Preschoolers getting more sleep = being calmer = 30mins break for teachers + easier time after nap time.
We went outside, ate our sandwiches or bought lunch from the canteen, and then played for the rest of the hour.
The whole "school lunch" thing in the US I find bizarre.
Though that was highschool. I can't remember middle/elementary well enough, though even then I really don't think it was an hour.