We know that ages 3 and 4, Grades 1 and 2, 4 and 5, and 7 and 8 are years of academic and intellectual explosion. Yet, Dr. Montessori observed that in the 6 year olds, 9 year olds (Grade 3s) and 12/13 year olds (Grade 6/7s) and 15 year olds (Grade 9s), their great work was social and emotional and lays the foundation for the next "explosion". She concluded that unless the social and emotional growth was addressed directly and effectively, rather than suppressed, academic growth could slow and suffer. Rather than fighting the social and emotional growth of the children in the third year of each sequence, Montessori encourages it. How? Instead of making those students in their transitional years the youngest of the children in a sequence, we make them the oldest and most mature in their group. We give them age-appropriate responsibility. We make them educational and civic leaders in this community.  The leadership of the older children has remarkable impact on the health of the three-year community they help lead, and it allows the oldest children in each cycle to stand tall with confidence during an uncertain time while internalizing the academic work of the first two years by sharing their knowledge and expertise with the younger students in the group. They become role models for the younger students, who long to reach their level of academic accomplishment and community responsibility.
We embrace the maxim, "You do not understand something until you can teach it," and giving lessons to the younger students in the group requires that the oldest children reduce complex concepts to their simplest elements and then convey them with clarity and understanding. If they cannot, it is clear that they need a lesson before going on! Thus, without fully realizing what they are accomplishing, our "third-years" internalize and consolidate the academic skills they have garnered for two years before exploding into the next three-year cycle.