Former CTU president Karen Lewis “really challenged the popular understanding about public schools,” said Robert Bruno, a professor at the University of Illinois at Urbana-Champaign. “She did take on the mayor. She did take on the school board, but Karen was speaking about public education and how public education had been put at risk. ... She wasn’t afraid to call out names and identify people in a very unvarnished, sometimes profane, but always profound way.” Brian Jackson/ Sun-Times file Karen Lewis was a fighter. As the president of the Chicago Teachers Union, she battled for the best contracts her members could get, even as she struggled against aggressive brain cancer.