The D.C. teachers union is supporting the strike by its counterpart in Chicago, where about 26,000 teachers are refusing to work after failing to agree on a contract with the city.

"Their fight is our fight!" reads a graphic posted to the Washington Teachers' Union's official Twitter account Monday morning, after "We support the Chicago Teachers Union."

In the second week of class, nearly 400,000 students were unable to attend school because of the strike. Working in the third-largest district in the nation, Chicago teachers and school officials couldn't agree on a new contract after 10 months of negotiations. Teachers say the impasse involves maintaining their health benefits and job security, as well as improving classroom conditions.

Officials with the D.C. union did not respond to requests for further comment.

The American Federation of Teachers, a national union, issued a statement supporting the Chicago teachers, as well. AFT President Randi Weingarten said "numerous steps" left the teachers "feeling disrespected, not the last of which was the district's unilateral decision to strip teachers and paraprofessionals of an agreed-upon 4 percent raise."

But the strike has been met critically by others concerned about the students' learning. The most high-profile dissident is Republican presidential candidate Mitt Romney.

"I am disappointed by the decision of the Chicago Teachers Union to turn its back on not only a city negotiating in good faith but also the hundreds of thousands of children relying on the city's public schools to provide them a safe place to receive a strong education," Romney said.

White House spokesman Jay Carney said President Obama was keeping tabs on the strike but not getting involved in the fight. "We hope that both sides are able to come together to settle this quickly and in the best interests of Chicago's students," he told reporters.

This is the first time the Chicago Teachers Union has gone on strike in 25 years. The city left about 140 schools open between 8:30 a.m. and 12:30 p.m to provide breakfast and lunch for those children who rely on free meals from the school district.