I haven’t been to school in decades but basically, the bus arrives when it arrives, maybe 30-45 minutes before school starts, and you want to be at the stop early for obvious reasons. It gets a little less stupid once you’re old enough to drive yourself, if you have a car or can carpool. But no way would a 20 minute commute be assumed.
UK average commute for high school is 25 minutes, and 3.4 miles [0], but a 30-40 minute doesn't sound awful on a bus, means leaving home 0800 so getting up 0740.
I've posted this before, but first bell was at 7:18, bus was at 6:30. I had it luckier in that I lived ~1 mile from school, but lived in an area where you couldn't safely walk. There were students that lived ~15 miles from school whose buses arrived ~5:45 to be able to make the 7:18 bell.
20 minutes from alarm clock to getting on the bus is unrealistic by an extremely wide margin. High school students typically shower, eat breakfast and get dressed at the very least.
I never had breakfast as a high school kid (still don't). 5 minutes for a shower, 5 more to get dressed and pick up bag, that leaves 10 minutes to get to bus stop.
