The Chicago Public Schools will not send layoff notices to thousands of teachers Monday as expected, but pink slips could hit central office workers this week, the Sun-Times has learned.

CPS is rolling the dice that it will reach a contract agreement with the Chicago Teachers Union by Feb. 1 to avoid layoffs altogether.

CPS chief Forrest Claypool had warned of layoffs on Feb. 8, the start of second semester, to plug a $480 million budget gap he blames on an unfair pension system.

The teachers contract requires 21 days’ warning with pay before layoffs. And teachers, as teachers do, did some math and landed on Jan. 18 as the day layoff notices would come.

Meanwhile, the CTU spread word on Facebook and to members via email of a layoff rally, gearing up for a mass action at 4:30 p.m. on the day after layoff notices go out, despite the many unknowns:

“WE DO NOT KNOW THE DATE, for certain, but we expect that the Board will announce layoffs of 1000, 2000, or 5000 CTU members,” the union wrote on Facebook. “However many they lay off will be too many! …Sign up your friends and colleagues. If Claypool and (Mayor) Rahm (Emanuel) lay us off, they’ll be kicking a hornet’s nest!”

It added in an email to members over the weekend, “As we approach the last three weeks of the semester, CTU members — and, indeed, the entire city — have been on pins and needles waiting to see whether CPS will demand that the wealthy and the banks pay their fair share to our schools or whether they will lay off hundreds or even thousands of educators, making students and those who serve them pay for the poor decisions of the mayor’s handpicked Board of Education.”

District spokeswoman Emily Bittner wouldn’t comment on layoffs except to say that negotiators are “focused on reaching the best agreement for Chicago’s teachers and children, and they’re working diligently in good faith to arrive at a fair contract that would prevent midyear teacher layoffs.”

On Monday, when classes are canceled for the Martin Luther King holiday, CTU leadership and its signature “big bargaining team” of about 40 teachers, counselors and other school workers will meet for a session with the Board, vice president Jesse Sharkey said.

“We’re taking this seriously right now,” he said Friday. “We’ve got our big bargaining team coming in on a holiday, and we’re trying to see if there’s a deal here. So far, there isn’t.”

Negotiations to replace the contract that expired June 30 have stepped up in the new year, taking place now daily instead of the Thursdays of past months. Claypool himself has attended some. CTU president Karen Lewis is in many as well.

Sharkey also cast doubt on original layoff estimates of thousands of his members.

“Everyone knows that if you tried to lay off 5,000 people in the middle of the school year, you would crash and tank the schools, and if you did that, you would only get halfway through their claimed deficit. So no, I don’t think that any of us think (Claypool) was really going to do it,” Sharkey said. “But I don’t have any doubt that they’re contemplating making cuts.”