Big-city mayors and U.S. Education Secretary Arne Duncan during a panel discussion today in Washington, D.C.

Last week, Chancellor Dennis Walcott spent Friday morning cautioning reporters not to take the city’s Teacher Data Reports too seriously. The city was releasing the information only because news organizations had won a legal battle for it, he said.

This morning, after a week in which Mayor Bloomberg defended the release, Walcott revised his message.

“It’s all about accountability,” he said, appearing on a panel in Washington, D.C., with Bloomberg and the mayors and schools chiefs of Chicago and Los Angeles.

“It’s all about accountability,” Walcott added. “And as the mayor indicated, parents have a right to have this information. What I’ve been trying to do is making sure that the entire New York City community understands that this is a limited piece of information and they have to view the teachers in their full context.”

Bloomberg jumped in to rebut philanthropist Bill Gates’ argument, made in a New York Times column just before the release, that no other industries release the results of employee evaluations.

“Incidentally Gates does give information at Microsoft to the people that need it, namely the managers to the people being evaluated,” Bloomberg said. “In our case it’s the principals and the parents who need that information. So we’re not doing anything differently from what Microsoft does.”

The other mayors on the panel — Chicago’s Rahm Emanuel and Los Angeles’s Anthony Villaraigosa — also said they were working to get more information into the hands of parents. But neither said volunteered that they would release performance data for individual teachers.

Instead, Villaraigosa said he was hoping to add letter grades to his city’s school report cards, as New York has done, so parents can make more informed school choices. Emanuel said Chicago would also copy some New York’s initiatives by adding five career-oriented high schools based on a city model and offering bonuses to principals who opt to work in struggling schools, similar to the city’s Executive Principals program.

Bloomberg said the city’s school reform efforts had more than paid off. ”We have closed the gap between black and Latino kids and white and Asian kids,” he said. “We have cut it in half.”

And Bloomberg offered a strident defense of testing moments after U.S. Education Secretary Arne Duncan, who also appeared on the panel, said the Obama administration was trying to reduce the emphasis on tests.

“This business of teaching to the test is exactly what we should do, as long as the test reflects what we want them to learn,” Bloomberg said. He added, “The tests that we do are in the children’s interest and in the teacher’s interest.”

Bloomberg cited a Vietnam-era protest song to make the case that school reform should not turn its back on testing.

“Pete Seeger had a song, ‘knee deep in the big muddy and the big fool said to push on.’ Without testing that’s exactly what you do,”Bloomberg said.

The Seeger song, “Waist Deep in the Big Muddy,” came out in 1967 as President Lyndon Johnson was escalating U.S. involvement in Vietnam. It tells the story of a platoon of soldiers who are wading in a river on their captain’s orders. But because the captain had navigated a different part of the river, he tells them to wade farther, even as the water becomes unexpectedly deep and the sergeant suggests they turn back. It is only after the captain drowns that the soldiers return to the shore.

“We were lucky to escape from the big muddy when the big fool said to push on,” Seeger sings. He goes: ”I’m not going to plant any moral, I’ll leave that for yourself … But every time I read the paper them old feelings come on. We’re waist deep in the big muddy, the big fool says to push on.”

Bloomberg’s full comments about testing are below:

We have a saying that in God we trust — everybody else has to bring data. And I know of no ways for a teacher to know whether they are getting through to the child and whether the child understands and is making progress without testing those children. And this business of teaching to the test is exactly what we should do, as long as the test reflects what we want them to learn. If the test is can you read, yes, you should find out whether they can read by testing them! And the tests that we do are in the children’s interest and in the teacher’s interest.

We want to walk away from responsibility because sometimes the tests show that we aren’t doing a good job, so, “Oh, I dont want tests.” Sometimes the tests show that we’re not devoting enough monies to the system, or we’re devoting too much money to the system. I know of nobody in this room that doesn’t get tested. You go to American University, you get tested. You [Mitchell] get tested — it’s called ratings. We get tested at the polls and with the press every single day. And this argument that we shouldn’t find out whether we’re doing a good job is just ridiculous.

… Pete Seeger had a song, “knee deep in the big muddy and the big fool said to push on.” Without testing that’s exactly what you do. And we are taking away the birthright of our children … Every time that we say oh we’ll test next year or two years from now or three years from now, you’re taking some kids and youre sending them out into the real world with lack of skills and they will never catch up.