The only con I can think of, is that you over stress the kid and they end up getting sick or hurt from moving too much. Otherwise, it is a good thing as everyone needs to keep moving.
I don't see any reason why it should be offered in school. In my country, PE classes are offered from first year high school to second year college. Though in college, there are different course, say freshmen will take track and field and sophomore will take the group sports etc. It will enhance students physical strength.
My nieces just 2 and 3 years old have Thursday mornings as PE sessions. The kids run and jump. I see all pros to this as it helps the kids not to be lethargic, especially all those overfed obsessed kids.