On the YAHOO! ANSWERS website, the question was asked, "St. Augustine said that the Church is a 'school for sinners.' What did he mean by that? Give examples please."
Below is an answerer's response, including references to St. Francis and Matt Talbot.
"This quote of St. Augustine's is intended to show that the Church is a place where people can go to change their life from sin and toward holiness. The Church has the power and authority to guide and help a person become holier. A common misconception of Catholic and other Christian churches is that the people in them should be perfect. This is not the case. St. Augustine recognized that when Jesus said he came to help the sinner and sick, not the righteous or healthy, this meant that the Christian way of life helps people become holier, but that this process can take a lifetime.
In this way, the Church is like a school, where God provides life lessons that enable a person to make choices to do God's will and to learn from their mistakes. As a sinner, say a person has the habit of stealing. Through prayer and the sacraments, like Reconciliation, the person can draw on grace and change their habits. The vice can be changed, through God's grace acting in the person, to virtue. Merely by accepting Jesus as Lord does not mean their bad habits go away. Rather, continued participation in the Church gives people the chance to open themselves to God's grace, which will then show in their changed lives and attitudes. The Church helps us "put on the new man" which is Christ (as St. Paul notes).
God provided the Church as a way to carry on His work in His name, and with His authority. The sinner participates in the Church, which has the power and tools, such as the sacraments, which bestow God's grace on the sinner. In the Church, the sinner has assurance that he or she is receiving grace to help them grow and mature in holiness. Outside the church, a person "may" receive grace, but there is not an assurance. Only through the Church does God assure that there is guidance without error.
The lives of the saints are excellent examples of this schooling process. For each saint, like us, there were crosses (weaknesses) to bear. Some were physical and some were spiritual. By turning to God in his Church, each saint confronted himself/herself and overcame their vices, sins, and weaknesses. God's grace did the work in the person, and the Church provided the opportunities to administer the grace and provide the knowledge a person needs to know God and open his or her life to Him.
Saint Francis for example, was young and sometimes vain man. His conversion transformed him over time to become humble and to serve the poor and needy.
Other people, like Matt Talbot of Ireland, changed from vices like alcoholism to become en example of holiness. Matt Talbot is not a saint yet, but is up for canonization.
As St. Augustine noted, The Church acts as a school for sinners, giving them assured channels of grace, the knowledge of God and themselves, to become holy and better people."