i'm an advocate of what i call anarchist schooling, which eliminates the classroom/grade system and allows students to work their way through the curriculum at their own pace, without the need to conform to the speed of a group. some kids will get through elementary school in six months; others will take 15 years. i'd still put teachers in classrooms and send kids to school, but the schools would be open 24/7 and the parents would decide when to send them based on their own schedules.
that aside, if we're to force people to conform to set one-size-fits-all schedules and ram kids into grade levels (and then push them through...), the school day ought to run longer, from 8:30 am to 17:30 pm, thereby eliminating or minimizing the need for parents to pay for after-school childcare.
like, that should be an aim, not a drawback.