Chicago Mayor Rahm Emanuel defended the Noble Charter School network for charging students fees for misconduct.
School activists accuse the 10-school network of collecting almost $200,000 last year by fining students to attend detention or behavior classes, and nearly $400,000 since the 2008-2009 school year.
Emanuel said parents choose to send their kids to Noble schools because of their college preparation results.
"I do not want anyone to lose sight of a graduation rate, a college attendance rate and a success rate that we would all marvel at if it became the standard for the entire system and system wide," said Emanuel.
Noble Network head Michael Milkie acknowledged that the schools have collected hundreds of thousands of dollars in fines, and he said the money is used to run disciplinary programs.
Nearly 90 percent of students who attend Nobel Charter Schools come from low-income families.