A group that describes some of the remarks as inappropriate posted an edited version of the speech on YouTube.
Since her election as the union's president last year, Lewis has gained a reputation as a fiery speaker and advocate for teachers. In the context of the 35-minute speech to educators and union members, she lived up to that reputation. Watch the entire video of Lewis' speech
"Teaching and learning is the most important thing we do," Lewis said in the speech.
But some critics say she also crossed the line when she mocked U.S. Education Secretary Arne Duncan's speech.
"Education is a civil rights issue of our time. Now you know he went to private school, 'cause if he had gone to public school he would have had that lisp fixed. I know that was ugly, wasn't it? I'm sorry," said Lewis.
The Education Action Group, which advocates school choice, is circulating the YouTube video as an example of problems in public education.
"We attempt to educate our children that that's not how you should act. And yet, the adults, the teachers union leaders, that's precisely how they're acting," said Kyle Olson, Education Action Group.
CTU spokesperson Stephanie Gadlin issued a statement saying, "the observations she made about herself and other public figures were an attempt at humor and candor before a live audience...they are being presented out of context in order to shift the focus from bad public policy decisions in education to attacks on her character."
During the speech, Lewis also spoke about casual drug use during her years as the only African-American woman at an Ivy League college.
"People are impressed. Let me tell you, I spent those years smoking lots of weed, self-medicating," said Lewis.
Terry Katsulis spent 42 years in the Chicago Public Schools as a teacher and principal. He is concerned Lewis is sending the wrong message.
"It was completely inappropriate for the president of a union with over 30,000 teachers to speak something like that," said Katsulis.
According to the teachers union, Lewis called Duncan Monday afternoon to explain her comments. She says she has learned that she should never let frustrations get in the way of carrying out her responsibilities as a leader.