(NBC Chicago) -- For the first time in 25 years, teachers in the country's third-largest public school system hit the picket line.
After a weekend of unsuccessful 11th hour contract negotiations, the Chicago Teachers Union made good on its promise to walk out on more than 400,000 students at 675 schools.
"We have failed to reach an agreement that will prevent a labor strike," Chicago Teachers Union President Karen Lewis said.
The strike follows more than a year of slow, contentious negotiations over salary, health benefits and job security after the school board unanimously voted last year to cancel teachers' 4 percent pay hike in the final year of their contract.
