(CNN) More than 25,000 Chicago teachers will return to school on Friday after an 11-day strike in the nation's third-largest school system ended, with a tentative deal ensuring millions of dollars to reduce class sizes and bring more nurses and social workers on campuses.

Classes will resume for some 300,000 public school students, Mayor Lori Lightfoot said Thursday in announcing the strike's end.

Chicago Public Schools and the Chicago Teachers Union reached an agreement that will result in five days of classes being made up. The union wanted twice as many days to be added to the calendar but settled on the compromise, both sides said.

Late Wednesday, the union agreed to the five-year contract agreement with CPS but the union said it wanted a firm commitment that the days the students missed would be added to the calendar.

The compromise marked a reversal of Lightfoot's initial position. She had said teachers would not get the days back from when they were on strike and that pushing the issue would just keep students out of school longer.

"In the interest of our students and our parents who have been suffering, it was important to me to make sure that we got our kids back in class," Lightfoot said. "Enough is enough. And so, in the spirit of compromise, we agreed. It was a hard-fought discussion, took us a lot of time to get there but I think this is the right thing ultimately for our city."

Our students will be back in school. These are words I've been waiting and wanting to say for weeks now. This is what matters most. https://t.co/HXrotgR4UU — Janice K. Jackson, EdD (@janicejackson) October 31, 2019

In a tweet, CPS CEO Janice K. Jackson said: "Our students will be back in school. These are words I've been waiting and wanting to say for weeks now. This is what matters most."

BREAKING: We have reached an agreement with the mayor and CPS to make up five days of student instruction. Students and educators will return to classes tomorrow. #CTUSEIUstrike #whenwefightwewin pic.twitter.com/p8zr9C6vgJ — ChicagoTeachersUnion (@CTULocal1) October 31, 2019

Union President Jesse Sharkey told reporters he was pleased that teachers will able to return to work.

"Frankly, it's been hard on teachers to be out this long. And it's been hard on parents to be out this long. It's been hard on our students," he said.

The deal must be ratified by CTU rank-and-file members. That vote takes place in schools 10 days after a strike is suspended, the union said.

Terms of the agreement

smaller class sizes and more case managers, librarians and other support staff in a city where many children face For nearly two weeks, union members picketed and rallied in the streets calling for demands such assmaller class sizes and more case managers, librarians and other support staff in a city where many children face poverty, violence or grief at a young age.

Here are some of the terms of the agreement that union members accepted late Wednesday:

-- Staffing increases, including 209 more social worker positions, which will allow for one to be placed in every school, and 250 more nursing positions by end of the contract

-- $35 million a year to reduce oversized K-12 classrooms

-- $2.5 million in recruitment and training

Lightfoot called the contract "historic."

"This has been a very hard and difficult journey," she said.

The strike's unintended victims

While the strike called attention to issues educators faced in the schools, there were a number of unintended victims

Many high school athletes, including tennis and soccer teams, have missed playoff and regional competitions during the strike. The Illinois High School Association forbids athletes from striking schools to compete during a work stoppage.

Football teams were in jeopardy of not being able to compete in the playoffs that start on Saturday.

If the strike dragged, counselors wouldn't have been able to send in transcripts for college applications. Many universities set Friday for early decision deadlines.

Teachers were at risk of losing their benefits.

"Health insurance coverage is based on being in pay status on the first day of the month, so we are covered for the month of October," the union's website said.

"If the Mayor chooses to cut health insurance effective November 1st, members (and their covered dependents) will automatically be eligible for COBRA."

COBRA offers temporary coverage of health benefits under certain circumstances . But it's often much more expensive than standard health insurance plans.

Victory for support staff

Chicago Public Schools reached an initial deal earlier this week with SEIU Local 73, the union representing school support staff.

"This is a victory for working people in Chicago and shows what is possible when we unite and take action," SEIU Local 73 President Dian Palmer said.

"The lowest-paid support workers who are the backbone of our schools are going to see raises that mean their families won't have to struggle living in an expensive city where costs keep going up," he said.