Learning by teaching outside the LdL-context

Sudbury schools
Sudbury schools, since 1968, do not segregate students by age, so that students of any age are free to interact with students in other age groups. One effect of this age mixing is that a great deal of the teaching in the school is done by students. Here are some statements about Learning by teaching in the Sudbury Schools:

    "Kids love to learn from other kids. First of all, it's often easier. The child teacher is closer than the adult to the students' difficulties, having gone through them somewhat more recently. The explanations are usually simpler, better. There's less pressure, less judgment. And there's a huge incentive to learn fast and well, to catch up with the mentor.
    Kids also love to teach. It gives them a sense of value, of accomplishment. More important, it helps them get a better handle on the material as they teach; they have to sort it out, get it straight. So they struggle with the material until it's crystal clear in their own heads, until it's clear enough for their pupils to understand."

Pupil-Team Learning: The Durrell Studies
In the 1950s Dr. Donald D. Durrell and his colleagues at Boston University pursued similar methods which they named Pupil-Team Learning. A year-long efficacy study in the schools of Dedham, Massachusetts, was published in the Boston University Journal of Education, Vol. 142, December, 1959, entitled "Adapting Instruction to the Learning Needs of Children in the Intermediate Grades" in which one of the authors, Walter J. McHugh, reported significant learning gains from the use of pupil teams.