When word circulated that Mr. Duncan planned to visit Kings Collegiate Charter School in Brownsville and Public School 65 in East New York, Randi Weingarten, the former head of the city’s teachers union, who is now president of the American Federation of Teachers, called him to express her disapproval. The principal of P.S. 65, Daysi Garcia, is one of only a few principals who have managed to have a teacher fired for incompetence. Several teachers have left since she took over several years ago, in part, union officials said, because they felt Ms. Garcia had treated them disrespectfully.

So at the union’s request, Mr. Duncan’s aides added a third school, Public School 214 in East New York, to his itinerary.

And it was there that he stood with Mayor Michael R. Bloomberg, pleading with Congress to pass legislation that he said would save thousands of teaching jobs. Mr. Bloomberg echoed the plea but focused his demand on the Assembly, calling on the Democrats there to raise the cap on charter schools.

“A number of reform ideas are under consideration by the State Legislature, and while I can’t talk about the specifics of any of them, I can say we share many of the underlying values they propose,” Mr. Duncan said. “The president has called on states to allow good charter schools to flourish while ensuring that there is real and equal accountability.”

As Mr. Duncan spoke at P.S. 241, he was flanked by Michael Mulgrew, the president of the United Federation of Teachers, on his far left and Lauren Harris, the principal of Kings Collegiate, on his far right. Neither of the two spoke during the news conference, but their supporters were battling from the sidelines.