TIL that the average school day in the US has about 6 hours, sometimes divided in six blocks of one hour each.
That sounds awful. Over here, the average school day has 4 hours (8 am - 12 pm or 1 pm - 5 pm), usually divided in 4 blocks of 50 min.
High School / Trade school combos usually have a day or two where it's 6 hours, but it's not that common, although some high school / trade school combos basically do all of high school in one shift and all of trade school in the other.
Even in university, it's usually still only one shift (with maybe one lab session on the other shift) spanning a total of 4 hours if you follow the suggested timetable. Who thought that making kids stay at school for 6 hours was a good idea?