It might be different between the U.S. States who knows but if you board a school bus with indecency they aren't permitted on the bus. Since most schools don't permit this type of exposure in correlation with the bus company they have a contract with I highly doubt they could be left like that. Now of this in modern-day times like the art suggests if you are willing to allow your daughter/ or son to go out to school with barely anything covering you that's it okay for them to be out like that you are most likely getting a few calls and a DCFS case on you. Mitsuri's parents are alive in the manga so there would be many questions about why they would permit such a thing.