Thousands of teachers walked off the job Monday in Chicago, the third-largest school district in the United States, after union leaders announced they were far from resolving a contract dispute with school district officials. The walkout posed a serious challenge to Mayor Rahm Emanuel, and by extension to the US Secretary of Education, Arne Duncan, who as CEO of Chicago public schools initiated many of the programs that teachers say are now driving them to strike.

“This is not a strike I wanted,” Emanuel said Sunday night. “It was a strike of choice.… it’s unnecessary, it’s avoidable and it’s wrong.”

For more on the choice to strike—I’m reposting here my conversation with Chicago teacher Jennifer Johnson, who addressed the Labor Notes conference in the city in May. Johnson teaches history at Lincoln Park High School in North Chicago, a diverse public neighborhood school that also has selective enrollment. Johnson’s father and grandfather were both teachers. She loves her job, but she’ll strike if she has to, she told me then. It’d be “doing justice” to her pupils. For the original post, on the run-up to today’s strike, go to “Chicago Teachers Turn up the Heat on Rahm.”