I should probably have been clearer: the reason classes are often scheduled at the same time is because it’s impossible not to. You have some amount of staff, each of whom have to teach some amount of lower level and/or elective classes, and then you have a couple hundred students each of whom pick 5-7 (or whatever it is, I haven’t read the books recently) electives in whatever combination most appeals to them. The chances of not having a collision anywhere in the whole timetable are pretty damn low. Non-magical schools deal with collisions by forcing students with unpopular combinations to change one of their options (which is what my school did), or by offering a an extra class during lunch or outside regular school hours (which I’ve heard of other schools doing)
I should probably have been clearer: the reason classes are often scheduled at the same time is because it’s impossible not to. You have some amount of staff, each of whom have to teach some amount of lower level and/or elective classes, and then you have a couple hundred students each of whom pick 5-7 (or whatever it is, I haven’t read the books recently) electives in whatever combination most appeals to them. The chances of not having a collision anywhere in the whole timetable are pretty damn low. Non-magical schools deal with collisions by forcing students with unpopular combinations to change one of their options (which is what my school did), or by offering a an extra class during lunch or outside regular school hours (which I’ve heard of other schools doing)