USA: Typically for us, about 7-ish hours, I have to go in the building before classes start before then though, making it about 8 hours. Sometimes, we have half days, but they’re pretty rare. We have all our classes, they’re just very condensed 4-5 hours.
Here, we start at like 07:00 (Mondays 08:10 or so) and we end at 14:50.
Norway: 6-7 hours apparently, from 08:00-14:00 (2: p.m.) or 15:00. (3 p.m.)


We don’t have high school in Ireland.¹
When I was in secondary school in the early 2000s, the day ran from 09:00 to 16:00 Mon to The, and we finished an hour early on Fri. My sister’s school ran from 09:00 to 15:45 every day.
¹I am not being pedantic. Ireland, like Britain, has a two-stage system with primary (5 - 12/13) and secondary (12/12 - 18) schools, in contrast to the tgree-stage system found in France, America, and Japan.
Thank you for the footnote. Without that, it could also have been pedantry, or the German system, where secondary schools have postsecondary-like specialisations already.