They already have daycare picking the kids up. Now they have to drop the kids off, and the kids can't really do anything at daycare because they are quickly getting into the bus to get to school, then when off school there is less time to do anything before their parents pick them up again.
High school has sports and activities though. I know many families that use the sports team as if it were a day care. If they do sports the kids usually get out somewhere between 4:30 and 5:30. Where I live now, a lot of the high schoolers are in school 7:30-5:30. It’s pretty ridiculous, since they also have homework. Many high schools seem to be in the process of transforming themselves into juvenile prisons designed to keep teenagers away from the rest of society.
It’s not an analogy. One of school’s main purposes along with sorting and ranking and reducing their tendency to creativity and independent thought is day care.