My high school went from 8:30-4:00 M-F (non-negotiable) plus if you were in sports, dance team, cheer or band, you practiced starting at 7:00 AM or went until 5:30 every day during your season. We did not have things like late start to give teachers prep time, but if you are basing this in CA (I used to teach out there), that sort of thing is big, and kids in California don't have to go to school as many hours as they do in other states (in my experience). Like the school schedule out in California was 8:30-2:30, and every Wednesday, kids got out early at 1:00, which was a RIDICULOUSLY wonderful amount of teacher prep time considering what I was used to in other states.
Dances were not a big thing. Sometimes they would try to have one and then come on the announcements to cancel them the day before because they had sold less than 10 tickets. There was a prom in late spring. None of the events you described would ever happen at my school. Sometimes during football season they would have "spirit days" on Fridays and dress up like a theme (twins, wear blue, cowboy day, crazy hair) but maybe 5% of the school participated, if that. This was public school, 2,000 students.
Dances were not a big thing. Sometimes they would try to have one and then come on the announcements to cancel them the day before because they had sold less than 10 tickets. There was a prom in late spring. None of the events you described would ever happen at my school. Sometimes during football season they would have "spirit days" on Fridays and dress up like a theme (twins, wear blue, cowboy day, crazy hair) but maybe 5% of the school participated, if that. This was public school, 2,000 students.