Ignatius 
came rather unexpectedly to the decision to accept an invitation to establish the first Jesuit school for lay students (at Messina in 1548) but once he made the decision other Jesuit schools quickly opened in Palermo, Vienna, Rome, and elsewhere. By Ignatius' death in 1556, some 35 were in existence. Two hundred years later there were more than 800 Jesuit schools in Europe, Asia, and Latin America. They constituted the largest system of education before the modern era of public schooling and the only truly international one. Responding to the criticism that instruction in these schools was haphazardly organized, Jesuit educators asked for a document that would be a comprehensive "plan of studies" that would serve as a guide. After a number of trial versions, the authoritative Ratio Studiorum, to give it its common title, was issued in 1599.
Not a tract of educational philosophy, the Ratio was a compilation of directives for the conduct of each official in a Jesuit school. Nonetheless, a theory can be read into the details of each job. Discussions of the principles of Jesuit education embodied in the Ratio abound. Here is a brief list of useful articles:
Gabriel Codina, S.J., "Our Way of Proceeding in Education: The Ratio Studiorum," a commemorative essay on the Ratio Studiorum that appeared in Educatio S.J. (May 1999), a publication of the Secretariat for Education of the Society of Jesus in Rome.
An introduction to the Ratio Studiorum by John W. O'Malley, S.J.
The 1911 Catholic Encyclopedia article on "Ratio Studiorum" with a brief survey of its history.
Claude Pavur, S.J., "The Document that Got Specific About Jesuit Education: The Great Ratio at 400"
Fordham University organized a celebration of the 400th anniversary of the publication of the 1599 Ratio. The papers from that conference were published in The Jesuit Ratio Studiorum: 400th Anniversary Perspectives, ed. Vincent J. Duminuco, S.J. (Fordham 2000).
The Digital Library Initiative of Boston College Libraries prepared a web site that has useful links to material about the Ratio, including the translated text of the Ratio, a historical essay by John O'Malley, S.J., and materials related to a former exhibition held at The Burns Library at Boston College that highlighted early editions of the Ratio: http://www.bc.edu/bc_org/avp/ulib/digi/ratio/ratiohome.html.