1) Schools are about to be done for the academic year, so they're effectively shut down until August anyway. It wouldn't make sense to re-open schools for less than a month.
2) For better or for worse, we've conditioned people to be wary of contact with other people. A movie theater that's 10% full is still hemorrhaging money, perhaps worse than if it was closed entirely (no payroll costs/etc).
I'm not sure what the breakdown is, so this could certainly be hyperbole, but it's entirely possible that people will just feel uncomfortable doing things with groups of >10 until a vaccine is available. A restaurant with 25% of its normal business will likely still need to shut down, reduce staff, etc.
Sure, we may not have 22MM people filing for unemployment but it might still be 10MM, which is still extremely abnormally large.
All that to say, there's a real possibility that gradual re-openings don't actually accomplish anything because the root fear (i.e. catching covid-19) hasn't been resolved in the minds of many people, especially in dense urban areas.
Though it could make sense to re-open them a month early, health concerns permitting. They already got a "summer break" and can make up for lost time
My kid is absolutely still participating in school, and quarantine is pretty stressful for a kid. This hasn't been just loafing around, relaxing, and playing.
step 1) re-open elementary schools
step 2) re-open middle schools
step 3) re-open high schools & colleges
step 4) re-open all small businesses that do not result in gatherings of more than 2 people in one place, then 5, then 10, then 20, then 50
I'm not saying that's the right approach but there is certainly middle ground between current shutdowns and a total re-opening of society.