Labor Disputes Heating Up in Urban Districts, After Respite

After a lengthy period of relative harmony, teachers in several big-city districts are raising the stakes in collective bargaining battles.

Teachers in San Francisco and Oakland, Calif., have threatened to go on strike later this month, following strike-authorization votes by union members in both districts late last month. In Detroit, meanwhile, 1,500 teachers in more than 50 schools called in sick March 22.

Union officials say the developments in the three cities illustrate teachers’ frustrations on a variety of issues, including pay and working conditions, as well as pressure from federal mandates under the No...