Tentative deal reached in Chicago teacher strike

Teacher Jillian Connolly helps her daughter Mary study math problems while picketing on September 10, 2012 in Chicago, Illinois.</p>

Teacher Jillian Connolly helps her daughter Mary study math problems while picketing on September 10, 2012 in Chicago, Illinois.

A teacher strike that's shut down the third-largest school district in the US may be coming to a close.

The Chicago Teachers Union and the city's school board reached a tentative deal in the five-day dispute late Friday afternoon, a source familiar with negotiations told CNN.

More from GlobalPost: Chicago teachers strike for first time in quarter century

Talks are expected to continue Saturday morning, and an attorney for the teachers union said both sides hope to have a deal drafted by Sunday.

Students could be back in the classroom as soon as Monday, school board President Dave Vitale told NBC News.

More from GlobalPost: Chicago teachers strike: Let's break it down

Tens of thousands of Chicago teachers walked off the job for the first time in 25 years this past Monday after months of negotiations failed to product a new contract.

At issue are pay, benefits and a controversial set of reforms demanded by Mayor Rahm Emanuel that evaluates teachers based on their students' standardized test scores, the Chicago Tribune reported.

The union worries that more than a quarter of its teachers could be fired because they work in poor neighborhoods where students perform badly on standardized tests, according to Reuters.