One of their two founders, the Anglican clergyman Andrew Bell, claimed that this system of mutual pupil instruction provided an "intellectual and moral engine" of unrivalled power that would produce better scholars, better Christians and better workers.
Bell first introduced the system in Madras, where he was superintendent to the Military Male Asylum, a charity school for the orphaned sons of soldiers.
In 1797 he returned from India to England, as rector of Swanage in Dorset. His account of "An Experiment in Education, made at the Male Asylum of Madras" was published in the same year.
The 19-year-old Quaker, Joseph Lancaster, began his monitorial school at Borough Road, Southwark, in 1798. His book, "Improvements in Education", was published in 1803. Both men made bold, not to say extravagant, claims. Drawing on his experience at Borough Road, Lancaster advised that one master could teach 1,000 pupils in a single school.
Not to be outdone, Bell maintained that one master could supervise 10 such contiguous schools. Both systems relied on mutual instruction, in which older pupils, called "monitors" by Lancaster and "tutors" by Bell, taught those younger or less able.
Monitorial schools were conducted in a single room. The teacher sat at a desk on a raised dais, instructed the monitors and kept an overall eye on proceedings.
But it was the monitors who taught, kept order in the classes and made daily, weekly and monthly reports on attendance and progress. Although there was much regimentation in monitorial schools, rewards rather than punishments were the order of the day.
For example, Borough Road operated an elaborate system of merit tickets, and prizes of bats, balls, hoops, kites and tops were suspended above the schoolroom to encourage both monitors and pupils in their work.
Further reading: W.B. Stephens, "Education in Britain 1750-1914", published by Macmillan, 1998.