The simple truth that is that as they grow older most people will happily compartmentalize, and indeed people are very good at it. However, on it’s moderately worse than average days, school takes it to such an extreme of cutting up segments of your day into different modes of thought that it really is difficult to handle.
On top of that, in high school work quantity per class climbs higher and higher, and this is on top of the enormous load of extracurricular that many have piled on for the college admissions game (I won’t even get started on what I think of that). The workload for many students is beyond excessive, and if anything it continues to grow, not shrink.
By the time summer vacation comes, kids are worn out. I don’t mean this metaphorically. It’s the literal truth. By the end of a school year, a lot of high school kids are truly, physically and mentally exhausted. If school lasted much longer, a lot of us simply wouldn’t make it through the year. As it is, more than a few people don’t quite make it through finals. There’s a reason I had a grand total of one half of one substantial post in June.
And of course in the often hilarious, always over the top world that is high school drama, a few thousand exhausted, worn out, teenagers makes for a cycle of fights wearing people out even more, so they get into more fights with friends, so they’re more worn out, etc. And in the middle of this, the SATs and finals. All around, not a very good thing.
The point being, summer vacation comes just in time. For various reasons, keeping school going much longer just would not work. If it were extended, either kids would simply stop being able to handle it, or they would manage at a very real detriment to their health. Again, it sounds silly, but I say this completely seriously. High work load high schools especially leave kids utterly worn out by the end of the school year. There are arguments against the long summer vacation, but I think that it requires a very fundamental shift in how American schools operate in several different ways before it could be changed without very serious repercussions for the schools (not to mention losing things that can only be done with the long summer vacation). Give me that massive shift in American education and I’ll consider the arguments again. Until then, summer needs to stay.