No time off from mindless busywork which doesn't, by any stretch of the imagination, prepare anyone for the real world.
No time off from senselessly time-consuming homework. (Why is it that students are given homework anyways? In the real world, your boss doesn't generally give you 'homework'; you work your 8 hours and you're DONE FOR THE DAY.)
No time off from cruel and sadistic bullies.
No time off from incompetent and disinterested teachers.
No time off from the mind-numbingly uncaring bureaucracy of the school administration.
No time off from waking up before dawn to trundle out to the school bus, alone and half-awake.
I'm 33 years old, and I look back at my school years as some of the worst times of my life. The suggestion of eliminating the summer respite would only make an already grueling and unpleasant period of every person's life significantly worse.
Now, there ARE ways to improve our school system. They don't involve adding more time to the school experience. They involve, among other things, tailoring the curriculum to the needs of each student, reducing the focus on mindless drilling for standardised tests, reshaping the curriculum to focus on useful real-world skills, transplanting money currently spent on sports (which should have no place in an academic environment anyways) and other non-academic things such as ROTC into better textbooks, better teachers, and perhaps even undoing some of the damage idiot parents in this country routinely do to their children (such as teaching them that Earth is 6,000 years old and was created in six literal 24-hour days, for example). They also involve treating students like human beings and not mere items on an assembly line, and ensuring that every student is treated with dignity. (The epidemic of school bullying needs to end NOW.)