I'll jump on the bandwagon and say that you don't need expensive classes and camps to enrich your child. We live in an area overflowing with opportunities - many of which are free.
Go to the Smithsonians. But don't just wander around the museums (although you should do that too!) They have tons of events for kids and a lot of them are totally free:
http://www.si.edu/Events
Go to the library. But don't just check out a book. All the libraries around here have a ton of activities and events - again, almost all for free. (A quick google search will find your local library system and all their events)
If you're in MD and can afford it, get a membership to the Maryland Science Center. Another great museum option, with lots of fun members only events.
Go to some of the many fantastic nature centers around here. Many of them cost some money, but only a few bucks. Find the one closest to you here:
http://www.chesapeakefamily.com/fun/fun-stuff-to-do/5553-7-nature-centers-kids-will-love-in-the-baltimore-annapolis-area
Check out your local community college. They often have classes for kids that might be a little more reasonably priced.
If you are going to pay for any ongoing enrichment, my #1 suggestion would be music lessons. Learning an instrument does SO much to help develop critical life skills.
It always makes me sad when I go to the library story time with my kids and see mostly other well-off, educated moms and their kids there. It is a FREE program, clearly designed to offer enrichment for little kids who need it. But the only people taking advantage are those who undoubtedly are already reading and singing and playing with their kids at home anyway. THAT'S the difference in the "good" schools. Involved parents who know how to use the available resources in their community. It doesn't take any money at all to do that.