Significant research has been done on the cognitive and academic outcomes of older-younger and peer-peer student relationships. Whether in a one-on-one setting or a setting in which responsibility for teaching is shared among members of a collaborative group, well-planned, well-organized, and well-executed student-student interactions have repeatedly shown positive evidence of student progress and learning This action research project differentiates itself from previous research in several ways because it focuses on motivational and attitudinal outcomes when every student in a classroom of eighth graders serves as a teacher of "new-to-everyone" content for three classes of younger students.
Check out this video -- we've done a lot of work with these schools. It is a nice piece to use in your consulting work -- to help teams envision what's possible.