I haven't had the chance to read the translations of Montessori's work, but I've read recently online that she briefly mentioned her idea of secondary schools involving adolescents gaining an education through their experiences working on a farm. Wikipedia has it cited as:
"The essential reform of our plan from this point of view may be defined as follows: during the difficult time of adolescence it is helpful to leave the accustomed environment of the family in town and to go to quiet surroundings in the country, close to nature." (1989, p. 67)Hershey Montessori School in Ohio seems to have taken that quote to heart when designing their school. They have received much recognition. Here is the Montessori for Everyone blog on Erdkinder (German for Earth Child) and the Hershey school. And here is NAMTA's David Kahn on the Hershey school and Colegio Montessori de Tepoztlan in Mexico.
Noted Montessorian Michael Olaf writes that adolescents need to spend time working with money, finding themselves, and trying different unpaid apprenticeships.
I'd like to get more of an idea of some existing Montessori secondary schools. Perhap they will give me some insight or inspiration. I'll create my list here.
Finally, NAMTA published a journal titled The Montessori Adolescent Analysis in Retrospect that I'd like to get a chance to read sometime (although I'm curious what they mean by "in retrospect"). They also host a course called The AMI Montessori Orientation to Adolescent Studies (hosted at the Hershey campus). I'd really like to attend after I get my Elementary I and II license.
EDIT (2/29/12): Montessori Muddle is a great blog I found that advertises itself as "Middle and High School ... from a Montessori Point of View." From the looks of it, the author talks about a little bit of everything. I can't wait to get reading.