CHICAGO (AP) — A threatened strike by Chicago teachers would test a strategy employed by a growing number of urban teachers unions who think transforming contentious contract talks into discussions about class size and student services wins public support and can make a difference at the bargaining table.

Unions in liberal-leaning cities, including Los Angeles, have made a renewed push to use the strategy this year, emboldened by strengthened public support for teachers and their unions after 2018 walkouts and protests in right-wing states. Chicago’s last major teachers strike in 2012 has been cited as an inspiration by other unions.

Now Chicago teachers are returning to that strategy, aiming to get enforceable school district commitments on smaller class sizes and hiring more support staff. Without those and other commitments, they could begin a strike Thursday that would affect nearly 400,000 students.

If Chicago does strike, teachers around the country will be closely watching parents’ response to a walkout based on the unions’ social justice agenda, beyond state school funding or teachers’ pay, analysts said.

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