Elizabeth Warren on Tuesday joined the Chicago Teachers Union picket line, as teachers from the country’s third-largest school system move into their sixth day of striking and fourth day of cancelled classes. “The unions are how we have a voice,” Warren said amongst the striking teachers. “The unions are how we have power. The unions are how we make sure that the needs of every one of our children are heard loud and clear.” Warren is not the first Democratic candidate to show support for the union. Sen. Bernie Sanders (D-VT) attended a rally for Chicago teachers before the strike began, and Sen. Cory Booker (D-NJ) met with union members on Friday. Other presidential hopefuls, including frontrunner former Vice President Joe Biden, have voiced their support via Twitter.

The union is demanding more support staff for teachers as well as smaller class sizes. Chicago Mayor Lori Lightfoot, a Democrat, has urged the teachers to return to work while negotiations continue. “Beyond what we put on the table, there is simply no more money,” Lightfoot said. “Enough is enough. There is no further excuse to keep our kids out of school.” In reaction to Warren’s arrival, Lightfoot said she “would expect all Democratic candidates for the presidency to support workers. That’s who we are as a party.” Adding, “but at the end of the day, what’s going to get it done is what happens at the bargaining table.”