My suggestion would be to start with specific interests (either that he already has or seem like something he'd enjoy) and then look for a way to find people who share those interests. Don't pay attention to age.
Some places where we've had success:
Community chess clubs.
Attending community talks and concerts and striking up conversations there.
Hiring a tutor or find a mentor for a single project. It could be as simple as asking everyone you know if they know an adult who would like to talk about Kozol's book and see if any ongoing discussion evolves. Retired people (especially retired professors) can be a good group to mentor.
Also, is there any possibility he could attend a gifted camp?
