Class A

[major league]

I am new to minor league baseball. How would someone compare Class A baseball to a non pro league like a Stan Musial baseball league. I have never seen Class A but I have watched a couple of games in the Stan Musial league and have seen a few pitchers throw at a decent speed. I also hear that there are alot of ex college ball players in the S M league. Is there a difference. I was just curious.