This weekend, Chicago Public Schools reached a tentative agreement with its teachers to resume in-person learning later this week. The deal isn’t final, and it’s the latest in a series of tense back-and-forth between the city’s schools and its teachers union. The bitter fight in Chicago echoes other big cities. Shruti Singh reports that tensions have escalated coast to coast between unions fearing the spread of Covid-19, and local officials under pressure to get teachers back into the classroom.