During his visits to the poorer quarters of Rome, Calasanz had discovered a small parish school, which like other schools, accepted only fee-paying students. It was the school of Saint Dorothy, which is beyond the Tiber River. When the parish priest died, he received the school. There he educated both the poor as well as rich children whose parents could afford to pay an amount of money every month. A short time later, he suppressed both the monthly tuition and the certification of poverty for those who wanted to enter.

Later on, Pope Paul V opened the school to everyone but kept it tuition free. There are some who suggest that the term "pious" in Pious Schools" actually means "tuition free" and not "pious."

But perhaps his greatest innovation was overcoming racial and religious discrimination. Calasanz taught that discrimonation, whether based on social class, race or religion was wrong. Both Jewish and protestant students were admitted to his schools, where they were treated with the same respect as other pupils. Pious Schools were soon established in many other countries, and so great and universal was Calasan's prestige that he was even asked by the Turkish Empire to set up schools there, although at that time they were considered great enemies of the Church.