CHICAGO — Teachers took to picket lines Friday in a one-day strike they said was aimed at getting lawmakers to adequately fund schools in the nation’s third-largest district.

The walkout closed schools for nearly 400,000 students, who had the option of spending the day at “contingency sites” Chicago Public Schools opened at churches, libraries and school buildings.

Among those picketing outside Oscar DePriest Elementary School was special education teacher Brian Orlinsky, who said he hopes the walkout will be a wake-up call for Chicago Mayor Rahm Emanuel, Illinois Gov. Bruce Rauner and other lawmakers.

“There’s not enough textbooks,” the teacher said. “There’s not enough technology that’s up to date and that’s working.”

Friday’s actions also could foreshadow a longer strike over a new labor contract, which by law can’t occur for several weeks.

The Chicago Teachers Union last went on strike in 2012, shutting down schools for more than a week before reaching an agreement with Emanuel. That contract expired in June, and the negotiations for a new one have been going on for more than a year.

Emanuel said he agrees more money is needed for schools, and particularly for districts like Chicago’s that serve poor students. He urged the union to join him and CPS in lobbying the Legislature rather than closing down schools, noting many students depend on CPS for meals and other help.