Duncan said that, while there had been improvements in education over the last few years, "we have to get dramatically better as a country" on the issue.
Danza, who spent a year teaching English to sophomores at Philadelphia's Northeast High School for the A&E reality-TV show Teach, drew loud cheers from students when he talked about his experience at the school.
Teaching the students "was the greatest thing I ever did in my life," Danza said.
Asked whether he planned to do more teaching, Danza said, "I'm not sure what I'm going to be doing . . . but I think there is more teaching in my future."
The program, shown at 10 p.m. Fridays on A&E, chronicles Danza's work as a first-year English teacher to a class of 26 at Northeast High, the district's largest school.
Asked why he would not be back to teach at Northeast next year, Danza said, "The show is not doing that well. . . . It didn't work out as well as it could."
Linda Carroll, principal of Northeast, said Danza brought a lot of enthusiasm to the job.
"Slowing Tony down a bit was something we had to work on," Carroll said, adding that over the year, Danza "got better and better" at teaching.
Asked about the need for more minority teachers, Duncan said, "We want our teachers to reflect the diversity of our students. . . . We have to give [students] better role models and teachers."
Panelist Muhammad Al-Ahmar, a fifth-year teacher of mathematics at Northeast, said attracting minorities like him was important. "Kids need someone who can relate to them" in the classroom.
Al-Ahmar said he started out in another field, but decided on teaching after seeing a sign advertising the need for a substitute teacher. "That's when I knew I had to teach," he said.
A woman who described herself as a senior education major at Temple asked the panel, At what grade level do teachers have the most impact on students?
Diane Honor, a seventh-year teacher of fourth grade, answered, "The early years is when children learn to love learning."
Speaking before the panel discussion, Mayor Nutter noted that Philadelphia students' test scores have improved for each of the last eight years.
Nutter said teaching was one of the country's most important jobs.
"I had a teacher . . . someone who helped me through some tough times in high school," Nutter said.
The mayor said, "Ninety-nine percent of the time, it was a teacher who stepped up and made a difference" in a child's life.
Ackerman, who has spent more than 30 years as an educator, said: "There's nothing more satisfying than teaching.
"I spent 15 years in a classroom, and it was the most challenging," Ackerman said. "We are looking for teachers who not only know the teaching side . . . but who embrace the job of teaching."
After the Temple gathering, Duncan joined Gov. Rendell in an address at the Greater Philadelphia Chamber of Commerce.
Asked what was the most pressing issue in urban education, Duncan pointed to high dropout rates.
In Philadelphia, the district reported the dropout rate at 28 percent in 2009-2010.
The district's graduation rate is 58 percent in four years.
"I am very optimistic about the direction this district is going," Duncan said. "There's a lot of hard work ahead, whether it's better engaging or figuring out how to get the hardest-working teachers and principals to those communities. . . . I feel very optimistic about addressing this challenge in Philadelphia."
Rendell said quality early-childhood education was a key to reducing the dropout rate. When children lack prekindergarten, full-day kindergarten, and smaller classes, "they fall behind by middle school."
Contact staff writer Vernon Clark at 215-854-5717 or firstname.lastname@example.org.