Wikipedia
The Monitorial System was an education method that became popular on a global scale during the early 19th century. This method was also known as "mutual instruction" or the "Bell-Lancaster method" after the British educators Dr Andrew Bell and Joseph Lancaster who both independently developed it. The method was based on the abler pupils being used as 'helpers' to the teacher, passing on the information they had learned to other students. The Monitorial System was found very useful by 19th-century educators, as it proved to be a cheap way of making primary education more inclusive, thus making it possible to increase the average class size. Joseph Lancaster's motto for his method was Qui docet, discit -- "He who teaches, learns." The methodology was adopted by the Roman Catholic Church in England and Wales, and later by the National Schools System.
The system is not entirely unlike the way professors, assistants and tutors work together in university education.
The Monitorial System, although widely spread and with many advocates, fell into disfavour with David Stow's "Glasgow System" which advocated trained teachers with higher goals than those of monitors.