At the White House, spokesman Jay Carney said Obama was monitoring the situation in his hometown but was not itching to take on a role in the dispute.
"We hope that both sides are able to come together to settle this quickly and in the best interests of Chicago's students," Carney told reporters.
The move by 26,000 teachers and support staff affected almost 400,000 students. It was the latest flashpoint in the public debate over public employee unions that have roiled politics in Ohio, Wisconsin and beyond.
Obama political aides in Chicago criticized Romney for seeking advantage and pointed to Romney's repeated campaign statements that class sizes do not impact students' education.
"Playing political games with local disputes won't help educate our kids, nor will fewer teachers," campaign spokesman Ben LaBolt said.
Emanuel, Obama's former White House chief of staff who is on the opposite side of the city's teachers in negotiations, was more direct in dismissing Romney.
"While I appreciate his lip service, what really counts is what we are doing here," he told reporters. "I don't give two hoots about national comments scoring political points or trying to embarrass - or whatever - the president."
Romney looked to tap into parents' concerns nationally with the dispute in Illinois, a state heavily favoring Obama in the fall elections.
"Teachers unions have too often made plain that their interests conflict with those of our children, and today we are seeing one of the clearest examples yet," Romney said in his statement. "President Obama has chosen his side in this fight, sending his vice president last year to assure the nation's largest teachers union that 'you should have no doubt about my affection for you and the president's commitment to you.'"
Romney was quoting Vice President Joe Biden's remarks to the National Education Association in 2011. But during his appearance, Biden acknowledged "not all teachers are created equal" and urged educators to be accountable.
"Incompetence in my profession - and in yours - reflects upon each and every one of us," Biden said. "So I don't have any doubt about your sincerity. And I don't have any doubt about your capacity. You should have no doubt about my affection for you and the president's commitment to you."
Obama, too, has urged accountability in teachers - moves that union leaders have opposed. For instance, Obama's administration has favored pilot programs that challenge current practices, rewarding schools who try new approaches and has pushed for longer school days.
Obama's education secretary, Arne Duncan, is a former head of Chicago Public Schools who pushed for changes that unions opposed.