There are many possible programs which cater to students looking to further their educations outside a standard classroom, either between high school and college, or at other times of life. I'm listing below just a few and their websites. Some cost quite a bit, others are more in the line of volunteer opportunities that cost little to the participant.

National Outdoor Leadership School- NOLS
http://www.nols.edu/

The Center for Interim Programs, LLC
http://www.interimprograms.com/

This program has one headquarters in Cambridge and it's possible to go meet with them to discuss the possibilities. In their case, the cost greatly varies, depending on what a student wants to do.

City Year- volunteer opportunity
http://www.cityyear.org/

Dynamy internship years- more costly, but sound like quite an opportunity-
http://www.dynamy.org/

Student Conservation Association
http://www.sca-inc.org/

Americorps
http://www.americorps.org/