Where I am in the US, you can choose "Electives", which are side classes in subjects you're interested in, but you have to take Math (up to Algebra II), English, History, science, and 3 years of one foreign language or 2 years of 2, and two years of health and Physical Education. And we have 4 classes a day that we go to every other day. This and Last year I've only had one elective because I took two years of spanish last year (Meaning I had to go to spanish every day.) and this year I'm taking both Trig and Pre-Calc in the same year. Next year I'll have 3 spaces for electives though, since there's no every day classes I plan on taking and I won't have PE anymore. This whole thing starts in middle school, but is somewhat different in middle school than high school, scheduling wise.
Colleges are really annoying. The ones that aren't that good are especially so because they try to spam you to cover up the rest of the better colleges.