"And you could see potentially even more teachers being laid off, working conditions for teachers becoming even worse and potentially for more strikes," he said.
The president added that under his administration, "what we say to school districts all across the country is we will provide you with more help as long as you're being accountable, and as far as teachers go, I think they work as hard as anybody, but we also want to make sure that they are having high standards of performance in math and science."
Money was not a significant issue in the Chicago strike. Mayor Rahm Emanuel secured an extension of the school day and empowered principals to hire the teachers they want. Teachers were able to soften a new evaluation process and win some job protections.
The day's campaign events showed the complexities of campaigning in Florida, a state that is home to large populations of seniors and of Hispanics.
Romney released a new television commercial designed to appeal to both groups.
It features Sen. Marco Rubio plugging the Republicans' plan to overhaul Medicare, a flashpoint in the campaign that Obama says could threaten future beneficiaries with high out-of-pocket costs.
Saying his mother is 81, Rubio declares in the ad: "We can save Medicare without changing hers, but only if younger Americans accept that our Medicare will be different than our parents', when we retire in thirty years.
"But after all they did for us, isn't that the least we can do?"
While Obama is likely to win the Hispanic vote overwhelmingly, he drew criticism in his appearances.
He said the lack of immigration reform legislation was his biggest failure as president and "not for a lack of trying or desire." He said he couldn't find a single Republican to help work on the legislation. "I'm happy to take responsibility for being naive here," the president said when pressed to admit he broke his promise.
Univision anchor Jorge Ramos interjected, "You promised us, and a promise is a promise. And with all due respect, you didn't keep that promise."
Obama drew praise from Hispanic groups earlier in the year when he announced a policy shift that will allow some immigrants brought to the United States illegally as children to avoid deportation.
Romney has been critical of the change, but has declined to say if he would reverse it if he wins the White House.
Associated Press writers Julie Pace and Jim Kuhnhenn in Washington and Steve Peoples in Florida contributed to this report. Espo reported from Washington.