They say some would be located in neighborhoods where CPS recently closed schools, and there are questions about the price tag.
The parents and aldermen want a vote delayed until the city council's independent budget office can do a cost analysis.
"CPS and the mayor have decided to take our tax dollars and give them to private charters to run our schools. Remember how well the privatization of the parking meters went," said Kerry Murphy, Raise Your Hand Coalition.
A spokesperson says providing "high quality education options is a priority for CPS," and that's why there are "rigorous standards" when approving charter school applications.