[rtkwe]

House keys and a bus though could work though for 90%+ of kids even in places with extreme weather [0] and you could have pre-school programs for the 10% that can't either because their too far for bussing or can't get themselves to the bus, eg those with assorted disabilities. You're right though the school start time is tied to it's function as free daycare for children so parents can work, COVID proved that is a critical part of schooling for the modern economy.

[0] Would need to provide more stops and ideally a better more consistent schedule so kids could get there just in time for the bus. Also for hot weather school picks up in the morning so even the hottest places aren't 110+ at pickup time.