From a Life of St Ignatius:
By now he was 33 years old and determined to study for the priesthood. However, he was ignorant of Latin, a necessary preliminary to university studies in those days. So he started back to school studying Latin grammar with young boys in a school in Barcelona. There he begged for his food and shelter. After two years he moved on to the University of Alcala. There his zeal got him into trouble,.... (he was trying to explain the Bible to his fellow students and teach them how to pray -- he got thrown into prison. He went to the University of Salamanca and the same thing happened))
At the University of Paris he began school again, studying Latin grammar and literature, philosophy, and theology. He would spend a couple of months each summer begging in Flanders for the money he would need to support himself in his studies for the rest of the year.
His school system grew partly by circumstance. He had started some schools to educate those who wanted to join the Jesuit order he had founded, but who needed more education. It soon became clear from communications from leaders and others that there was a need for schools for laymen as well. Eventually some secondary schools were founded as well as colleges.
He wrote of the schools he founded:
"From among those who are now merely students, in time some will depart to play diverse roles--one to preach and carry on the care of souls, another to government of the land and the administration of justice, and others to other callings. Finally, since young boys become grown men, their good education in life and doctrine will be beneficial to many others, with the fruit expanding more widely every day."