This is the bathroom at Sophie and Sam's school. It's right in the middle of the hallway leading to their classrooms, so we walk right by it every day, multiple times. Notice that there are like 10 toilets in there (you can only see four here, but there is one out of the picture + five more on the other side of the bathroom), so a bunch of the children can go at the same time, which is usually right after lunch, before recess, etc. The teachers send them in basically at the same time, so they're not always asking to leave during class.
Notice also that the doorway to the bathroom is like five feet wide. And notice also that there is no door to the bathroom. Yes there is in fact no door. You just go. No door.