Or at least that's what it was like for me. One of the things I loved to do was to code, and well, that sort of went out the window for the two years I was in high school because I'd be dead tired and in need of sleep every single night after the requisite extracurriculars and homework. My parents wouldn't let me drive to school in the morning because I'd get only a couple of hours of sleep a night sometimes and they didn't want me to fall asleep behind the wheel.
Even on weekends I didn't have time because I had to study for the classes I hated and do lame group projects where at least one member didn't do their fair share of work.
It's not necessarily a bad thing that HS trains (American) kids to work so well. Society runs on people doing (generally) repetitive work consistently. My early rejection of the system meant I got left out in the cold in terms of knowing how to do that. I did get a lot of 'soft' (i.e. cannot learn from books) computer/cs/systems knowledge out of what I did spent my HS years doing, though.
I am a bit biased because I found most of my pre-university studies boring. I also didn't fit in with the other students while I was in middle school and high school.