> One of the main purposes of school is child care, as we’ve observed through this pandemic, so schools must open when most adults go to work.

Schools usually close ~2 hours before the end of the conventional work day, though some (usually those for kids younger than teenage years) have optional after-school supervision programs available.

For teenagers, such programs are less common because the social consensus is that teenagers do not need constant adult supervision and can be unsupervised for a period of a few hours at a time.

you may be biased by your 9-5 job, but a lot of people work first shift, 7-3. i don't have any numbers to back it up, but since you made the claim do you mind?