In all honesty, I think they do a pretty damn good job of teaching you in BCT, and if you have no prior experience that's better because you haven't been taught how to incorrectly hold a weapon. Being taught by someone else will just give you bad habits that you will have to learn how to correct later. Best to start with the Marine Corps way.
My husband went to BCT having ZERO experience with actually shooting a weapon, and qualified as an expert marksman.
The first time you shoot your gun will be a grouping exercise at 36 yards, because the bullet at 36 yards is in the same place it would be at 300 yards. Then you'll shoot it at 100, 300, and 500 yards