You know his motto "what can it hurt?" (we all know the answer to this, but he's only concerned about whether it hurts him)
I'm only guessing, but from his perspective, he's screwed either way. If the economy doesn't open back up he's screwed, if he opens schools up and there's another collapse he's screwed, so he hitches his wagon on one thing: maybe schools can open up and there won't be mass reinfection. That's what some studies say and what other countries are doing (and we've had a ton of discussion here why a lot of that won't work here). If that works, then that's what he'll focus on. If it doesn't, he'll deflect blame like always.
Ideally you'd have the government lead the way with a bunch of studies, guidelines, and cautiousness. Maybe even a meeting to discuss the different options and hear dissenting opinions and address them. Have a bunch of studies on what transmission is like for asymptomatic kids: is it really that rare? Instead we got two hours of people saying how great he is and how his leadership is a "dream team."
It's also why he allowed/forced states to open up by not giving them any support and not extending extra unemployment (yet). And that hasn't worked out for him, but if it did... just like, hydroxichloriquine is probably not the cure-all, but if it was...