Chicago students are facing a potential strike by their teachers after Mayor Lori Lightfoot said the nation’s third-largest district will proceed with the reopening of elementary and middle schools.

Negotiations between Chicago Public Schools and the Chicago Teachers Union soured on Friday after the two sides could not come to an agreement about in-person learning during the COVID-19 pandemic. Students have worked online for nearly a year, prompting frustration among parents and hope that Chicago Public Schools would follow through with its reopening plan for Monday.