More than 60 years after Montessori's writings on adolescence, the third plane of development remains thrilling, pioneering work. As with all levels of Montessori education, this age requires wisdom and patience from its practitioners. Serving young people ages 12-18 also calls forth courage, integrity, and vision. During this plane, education takes much of its meaning from the grounding established in the second plane (ages 6-12). Adolescents in the third plane are refreshed and inspired by the big ideas of Cosmic Education, their relationship with others, and the world around them. It is a time in the human life cycle when adolescents are constructing their identities and are compelled to find their place in society. Their capacity to fulfill this need in a positive way depends on the creation of compassionate, sustainable schools that work for everyone. [This article was written with Barb Scholtz.]