Remind Me Again Why School Is Canceled For Two Weeks?

I know I'm going to get bashed for this, but here goes. School has been canceled for the next two weeks here in Montana and in many states across the country. I get the reasoning, I guess. I do have a few questions though.

Like what has changed between last week and this week for school-aged kids and teachers? If they are at risk this week, they were certainly at risk last week, weren't they? Also, if the schools are closed so that kids don't come in contact with the virus (or at least to lessen the chance), is it wise that those same kids are running around the mall, at the movie, in Walmart and at Winco (like the lady I saw today with 8 kids with her)?

I counted roughly 25 school-aged kids at the mall today, and 15 at Walmart (some with friends and some with parents). So, they closed the schools, but open the library as a daycare? Again, I thought the idea was to not have a bunch of kids in one location to lessen the chance of getting the virus? I don't make the rules, but it seems that if these students can be out with friends at these locations, why can't they be in school?