Dozens of Teachers from all three campuses walked off the job on Tuesday.
The union said it won an agreement for the right to open the contract for renegotiation shortly after the next school year.
"We're not here without the voices of parents and teachers advocating for students," said CTU in-house counsel Latoyia Kimbrough. "Parents and teachers speaking out doesn't mean they don't believe in the mission of Urban Prep. Parents and teachers are speaking out because they are the owners of the Urban Prep mission. This legacy is theirs, and they fought - we all fought - to make Urban Prep better."