CHICAGO (Reuters) - Thousands of striking Chicago teachers marched through the city’s downtown streets on Wednesday to demand smaller class sizes and more support staff in the second-longest walkout by U.S. public school teachers in recent history.

FILE PHOTO: Democratic presidential candidate Senator Elizabeth Warren yells as she visits a picket line of striking teachers in Chicago, U.S. October 22, 2019. REUTERS/Joshua Lott/File Photo

The third-largest U.S. public school system canceled classes for the fifth straight day for 300,000 students, who have been out of school and without after-hours activities since the system’s 25,000 teachers went on strike last week.

The Chicago Public Schools district said classes would be canceled again on Thursday, although buildings would be open and meals provided for students who needed a safe place to stay.

The Chicago Teachers Union called the work stoppage after contract negotiations failed to produce a deal on pay, overcrowding and a lack of support staff such as nurses and social workers.

Teachers banged drums, blew whistles and carried signs as they clogged streets during the morning rush hour. Vehicles stuck in traffic honked horns. One driver leaned out of her car near Willis Tower and told the teachers to get back to work.

The teachers then gathered at City Hall for a rally as Mayor Lori Lightfoot was set to deliver her budget address.

“We have kids that just want to learn and we just don’t have the resources to teach them,” Christina Morales, 32, said as she marched. “It’s not about the greed, it’s about the need.”

The strike is the latest in a wave of work stoppages in U.S. school districts. Teachers in Chicago and elsewhere have emphasized the need to help underfunded schools, framing their demands as a call for social justice.

The strike in Chicago is the longest teacher strike in the United States since Union City, California, teachers staged a four-day walkout over pay last spring. Los Angeles teachers held a week-long strike last winter over similar demands involving pay, class size and support staff.

Negotiators for the union and school system have been trading proposals since the strike began, while teachers have picketed daily in front of many of the system’s 500 schools and held rallies in downtown Chicago.

Democratic presidential candidate Elizabeth Warren joined striking teachers at a rally at an elementary school on the city’s West Side on Tuesday.

Lightfoot, who was elected in April, said the district offered a raise for teachers of 16% over five years and has promised to address class sizes and staffing levels.

She said the city could not afford the union’s full demands, which would cost an extra $2.4 billion annually - more than a 30% increase to the current $7.7 billion school budget.