CHICAGO (AP) — The president of the Chicago Teachers Union says it was “ridiculous” and “silly” for Illinois Gov. Bruce Rauner to call the city’s teachers “virtually illiterate.”

CTU President Karen Lewis said the comment Rauner made in a 2011 email “has nothing to do with reality.” Rauner’s assertion was revealed Thursday in emails Chicago Mayor Rahm Emanuel’s administration released under a court order to the Chicago Tribune. Rauner also wrote that half of CPS principals are “incompetent.”

A Rauner spokesman said the email was sent out of frustration at the pace of change in the public school system. At the time, Rauner was a large donor to an education reform group. He was discussing future investments.

Rauner is scheduled to sign legislation Friday involving student testing and teacher training in Chicago.