It was not immediately clear where Lewis got the 200 figure or when she believes such school closures might happen. But Chicago Public Schools spokeswoman Marielle Sainvilus called Lewis' claim "false," asserting that union leaders said a few days ago that 100 schools would close, and "I'm sure it'll be another number tomorrow."

"All Ms. Lewis is trying to do is distract away from the fact that she and her leadership are using our kids as pawns in this process," Sainvilus wrote in an e-mail.

Another point of contention involves the teacher evaluation system, Lewis said. The tentative contract would change it for the first time since 1967, taking into account "student growth (for the) first time," according to the school system. And teachers who are rated as "unsatisfactory and developing" could potentially be laid off.

Principals would keep "full authority" to hire teachers, and the school system will now have hiring standards for those with credentials beyond a teacher certification. In addition, "highly rated teachers" who lost their jobs when their schools were closed can "follow their students to the consolidated school," according to a summary of the proposed contract from Chicago Public Schools.

This contract calls for longer school days for elementary and high school-age students, 10 more "instructional days" each school year and a single calendar for the entire school system, as opposed to the two schedules now in place, depending on the school.

The pay structure would change with a 3% pay hike for the first year of the contract, 2% for the second year and 2% for the third year. If a trigger extends the contract to four years, teachers will get a 3% pay increase. Union members would no longer be compensated for unused personal days, health insurance contribution rates would be frozen, and the "enhanced pension program" would be eliminated.

As is, the median base salary for teachers in the Chicago public schools in 2011 was $67,974, according to the system's annual financial report.