CPS CEO Janice Jackson said that employee must clear a background check in order to go back into the schools.
Classes start on Tuesday.
The district started an effort to re-do background checks after a Chicago Tribune investigation that found some CPS employees who abused students had criminal backgrounds.
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"What we committed to is no individual who that has not undergone this check will be allowed to work back in our schools but I think it would be inappropriate to share information when we haven't completed the process," Jackson said.
There's no data from CPS showing how many workers have been disqualified by renewed background checks. However, CPS said the background check process is moving fast in a very short period of time.
Just over 44,000 district employees, which is about 99 percent of the district's workforce, have their fingerprints on file for review. About 220 full-time school-based employees who had not yet provided fingerprints are going through the district's disciplinary process this week. At the time of their disciplinary hearing, they will be fingerprinted on site if they had not already done so by the time of their hearing, according to CPS.
Meanwhile, CPS officials and Mayor Rahm Emanuel announced Wednesday morning that more Chicago elementary students than ever before are meeting or exceeding national standards for math and maintaining strong reading scores.
"One of the things I'm so excited about is literally less than a week from today, next Tuesday, that we begin the process of universal full-day, pre-K for every child in the city of Chicago," Emanuel said.