I've watched 30 kids get off at their school in the morning. It takes 15 seconds. By your logic, 30 stops adds 15 seconds to a bus's schedule, which is pants-on-head crazy.
Emptying a school bus completely is a lot faster than a city bus stop where people are simultaneously trying to get off the bus and then the new people are also trying to get on the bus and jockey for position and for a seat before the bus can start moving again
Emptying a school bus completely is a lot faster than a city bus stop where people are simultaneously trying to get off the bus and then the new people are also trying to get on the bus and jockey for position and for a seat before the bus can start moving again