Here's my district's high school schedule for an example, schedules vary slightly from district to district and state to state but this is reasonably representative:
http://www.rockfordschools.org/high-schools/rockford-high/da...
The breaks in my district are 6 minutes long, with five 71-minute class periods. You can't socialize much in 6 minutes, you have to get from one class to the next, which might be a 400m walk if you want to stop at your locker - walking through a dense crowd of people, with a 15 lbs backpack. Or 200m if you bring a backpack of 40+ lbs of books and binders for all your morning or afternoon classes, stopping by your locker just at lunch. Lunch is 24 minutes long somewhere before/in the middle of/after 4th period. "Zero hour" at the top of the linked schedule is if you want to take an extra class, eg. to accomodate state requirements like civics and communications while also taking year-long AP classes, performing arts classes, or doubling up on science/math electives beyond the minimum.
If you have an average morning bus arrival at 6:50, and add a sport that goes until 5:30PM, and are quick enough to have get your homework done in just an hour each night, it ends up being about the equivalent of a 60-hour work week...pretty rough on a 14-year-old child. But we're a Blue Ribbon Exemplary School! Top 250 in the nation! In spite of the flaws obvious in the schedule above, if my family is going to be in an American school system, and especially if we want them near extended family, friends, and my job, we're not going to do too much better than this: I bought a house in this district so my kid could get the same great education I did.