In a series of tweets posted around 9:30 p.m. Tuesday, the union announced that its leaders "can confidently report a 'yes' vote" to accept the agreement that has already been overwhelmingly endorsed by union leaders and delegates.
"Congratulations to all of our members, and thank you for remaining united, strong and powerful in the defense of public education," the union tweeted.
A few schools had yet to turn in their ballots as of Friday evening, but those "votes outstanding will not significantly alter the result," according to the statement from the union.
Approximately 72 percent of the votes counted so far have been in favor of the deal, union officials said.
It will take a day or two for detailed results of the referendum to be complied, according to the statement from the union.
The vote closes the door on a turbulent period in Chicago, marked by strife between the school district and the union that represents 30,000 teachers and support staff members It averts what would have been the second teachers' strike in four years.
Union President Karen Lewis had said she believed the agreement would be approved.
A comparison by DNAinfo of the tentative agreement inked Oct. 10 and an agreement rejected Feb. 1 by union officials found the union won significantly more resources for classrooms across the city while maintaining — and in some cases expanding — lucrative perks for teachers and support staff members by forcing CPS to renegotiate the pact while threatening to strike.
In total, the deal means between $300-$350 million more for schools, including compensation for teachers and programs for students, union Vice President Jesse Sharkey said.
CPS spokeswoman Emily Bittner has said the deal was "fair to both sides."
An eight-month deadlock over a new contract for teachers and support staff members ended once Emanuel agreed to heed months of calls from union officials, aldermen and parent-led group Raise Your Hand to give schools millions of dollars that had been collected by the city to spur the redevelopment of blighted areas.
Overall, CPS said the tentative agreement, once implemented, "will save $300 million over the life of the contract."
CPS officials did not provide an accounting for that figure, declining to provide more information until the pact was approved by union members.
CPS will continue paying the bulk of pension contributions for current teachers, who put 2 percent of their salaries into their own pensions, while CPS pays 7.4 percent.
CPS agreed to pay part of teachers' pension contribution in 1987 in place of a pay raise as part of contract negotiations.
That "pension pickup" cost CPS $170 million during the 2015-16 school year, officials said.
New employees will be required to contribute 9.4 percent of their yearly salaries to their retirement accounts. In return, teachers hired after Jan. 1 will get two raises of 3.5 percent — one effective in January and the other effective in July.
The tentative agreement also maintains raises based on teachers' experience and education. CPS initially proposed eliminating that structure entirely, prompting outrage from the union.
In addition, the new contract promises teachers 4.5 percent cost-of-living increases over four years, starting in 2018, with no pay raises during the 2015-16 and 2016-17 school years.
CPS officials expect health care costs to rise 6 percent a year, and had asked union members to pay 1.5 percent more of their salaries during the term of the contract toward their coverage in the rejected offer.
Instead, union members will pay 0.8 percent more for health care coverage, according to the tentative agreement.
But the tentative agreement revised that provision to allow laid-off teachers to earn their full salary for essentially an entire school year while waiting for a permanent position to open up.
The agreement also modifies the teachers' evaluation structure to be more fair and ensure that good teachers don't have to live with the "constant fear" of being fired, Sharkey said.
The tentative agreement also establishes more preparation time for teachers during the school day, and changes the system's grading policies.
In addition, the agreement also caps the number of charter schools at 127 campuses.
CPS officials agreed to earmark $7 million to hire teachers' assistants in kindergarten through second grade classes with more than 32 students, starting in January.
District officials will spent between $10 million and $27 million to provide after-school programs, counseling, social work and psychiatric services and medical clinics at 20-55 schools to be picked by a joint committee of union members and CPS officials.
Laurence Msall, president of the Civic Federation, a business-oriented government watchdog, has said he had a number of questions about the agreement, including how an early retirement incentive plan would work.
For it to be implemented, at least 1,500 teachers must agree to retire early at the end of this school year in return for an extra $1,500 per year of service to the district. Members of the support staff with 10 years of service will get an extra $750 per year of service if they retire at the end of the year.
The district's budget also relies on $215 million that the General Assembly and Gov. Bruce Rauner promised to give CPS in return for "pension reform."
That uncertainty has not been acknowledged by CPS officials, Msall said.