CHICAGO (CBS) — As the plan to close more than 50 Chicago Public Schools moves forward, the head of the Chicago Teachers Union said she has numerous examples of what can go wrong, and has gone wrong with previous school closings and consolidations.

WBBM Newsradio Political Editor Craig Dellimore reports CPS Chief Executive Officer Barbara Byrd-Bennett has vowed students relocated because of closing schools will end up at better ones.

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But CTU President Karen Lewis challenged that assertion.

“It’s not true, it would be lovely if it were true, but it is simply not true,” she said.

Lewis said school closings in Chicago never have worked to improve students’ education, even when displaced students end up at unquestionably better schools.

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Lewis said parents and others at receiving schools worry that incoming students will drag the school’s test scores down.

“So, if you go back and look at several of the schools where the consolidations have happened, you will find that the children are not welcomed. There have been hostilities,” she said.

CPS officials disagree.

Regardless, Lewis has said the CTU wants to register voters and train candidates in a bid to oust Mayor Rahm Emanuel in the next city election in 2015. The union also plans to seek out candidates for aldermen who would be more supportive of teachers and students.

“We have to stop waiting for other people to do our work for us, so we need to find candidates who are responsive to the entire city of Chicago, not just the downtown business interests,” she said.

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Lewis is the guest on this weekend’s “At Issue” program, airing at 9:30 a.m. and 9:30 p.m. on Sunday.