Chicago’s second charter school strike ended early Monday with the teachers union winning concessions on pay raises for teachers and paraprofessionals that will put their salaries on par with educators at non-charter schools.

Under the deal, reached overnight after two weeks without classes, the union said Monday that teachers at four Chicago International charter schools, known as CICS, will see an immediate 8 percent pay bump. Over the next four years, their salaries will rise more substantially.

Paraprofessionals will be brought up to district pay scales immediately, the union said.

Students and teachers at the four schools, are managed by Civitas Education Partners, will return to class Tuesday. CICS oversees 14 schools in all a complex organization that includes multiple managers.

The deal ends the the latest display of the Chicago Teachers Union’s organizing muscle ahead of several high-stakes contract negotiations, including contract with Chicago Public Schools that expires in the spring, and several other charter contracts still in talks.

The contract will apply only to the four schools that have a union and were on strike: Northtown Academy, Ralph Ellison, Wrightwood, and Chicago Quest. But a spokesperson for CICS said Monday that the organization was “committed to equity” across its other 10 campuses and is in internal discussions about how the bargaining will impact teachers and classrooms at its non-unionized schools.

CICS had warned during the strike that it could face bankruptcy if it implemented all of the union’s demands. In a statement Monday, the network said that the issue of “limited funding” was an “unfortunate reality in public education.”

“In order to pay for such a significant salary increase, we will be forced to make certain cuts and compromises,” the statement said. “For example, we will likely need to limit the number of instructional coaches, assistant principals and other valuable support staff members.”

The tentative agreement brings to an end a contentious nine-day strike that started with picket lines and escalated late last week when dozens of teachers blocked the lobby of the Loop high-rise housing the offices of accounting firm PricewaterhouseCoopers. The board president of CICS, Laura Thonn, is a partner in the Chicago offices of the firm.

Friday also was payday for teachers, who received substantially smaller checks than they would have had they been working.

The teachers union and CICS said that the tentative agreement also guarantees assistants in kindergarten, first-, and second-grade classrooms; paid parental leave for teachers; and a slightly shorter work day. The tentative agreement cuts the workday by 15 minutes but does not reduce instructional time, CICS said Monday.

One sticking point was also class size. The tentative agreement sets a “goal” of 28 students per class with a clause that limits class sizes to 30. Overcrowding at district schools has been a point of intensifying discussion this year, too, with a new report from the group Parents 4 Teachers showing that more than 1,000 classrooms in kindergarten through eighth-grade in Chicago have more than 30 students.

“We have finally won a contract that our schools, students, and our staff deserve,” said Jen Conant, a CICS Northtown teacher and member of the bargaining team.

The tentative contract will now go to the broader union membership for a vote.