Already Seneca told in his letters to Lucilius that we are learning if we teach (epistulae morales I, 7, 8): docendo discimus (lat.: "by teaching we are learning"). At all times in the school-history there have been phases where students were mobilized to teach their peers. Most of the time, it was in order to reduce the number of needed teachers, so one teacher could instruct 200 students. However, since the end of the 19th century, a number of didactic-pedagogic reasons for student teaching have been put forward.
Students as teachers in order to spare teachers
In 1795 the Scotsman Andrew Bell wrote a book about the mutual teaching method that he observed and used himself in Madras. The Londoner Joseph Lancaster picked up this idea and implemented it in his schools. This method was introduced 1815 in France in the "écoles mutuelles", because of the increasing number of students who had to be trained and the lack of teachers. After the French revolution of 1830, 2,000 "écoles mutuelles" were registered in France. Due to a political change in the French administration, the number of écoles mutuelles shrank rapidly and these schools were marginalized. It is important to stress that the learning level in the Bell-Lancaster-schools was very low. In hindsight, the low level can probably be attributed to the fact that the teaching-process was delegated entirely to the tutors and that the teachers did not supervise and support the teaching process.
Students as teachers in order to improve the learning-process
The first attempts using the learning by teaching method in order to improve learning were started at the end of the 19th century.
Selective descriptions and researches
Accurate researches are starting in the middle of the 20th century, however just as selective descriptions. The method received broader recognition starting in the early eighties, when Jean-Pol Martin developed the concept systematically for the teaching of French as a foreign language and gave it a theoretical background in numerous publications. 1987 he founded a network of more than a thousand teachers that employed learning by teaching (the specific name: LdL = "Lernen durch Lehren") in many different subjects, documented its successes and approaches and presented their findings in various teacher training sessions. From 2001 on LdL has gained more and more supporters as a result of educational reform movements started throughout Germany.