http://www.youtube.com/watch?v=XHCAfmL2U7I
This video helped me a bit about how A school goes. She goes into great detail about it. It was also posted about a month ago so it's pretty up to date.
As far as what you would be doing. It depends on where you get stationed to. Normally a lot of new HM's go to hospitals right after A school to get some experience before they do more intricate things such as getting stationed onto a ship.