I had good experiences with both the Chesapeake Sailing School at Port Annapolis Marina learning on a 22ft Tanzer keel boat and Mariner Sailing School on the Potomac River at Belle Haven marina on Flying Scots.
Both these schools have a laid back yet thorough approach for teaching new sailors the basics.
A good link on the topic...
Sugesstions on best place to learn on the Chesapeake
BTW~I took the long weekend course from Chesapeake Sailing School and thought it was great.
Both have rental programs for grads so one doesn't have to go full bore into ownership to enjoy.
We did that for about two seasons before settling on the boat we bought.