Students, teachers, the principal — nearly everyone at Northeast High School in Philadelphia was skeptical of Tony Danza, whose year teaching 10th-grade English was filmed for the A&E documentary series Teach: Tony Danza.

They assumed the former Taxi and Who's the Boss? star was unqualified to teach, though he has a degree in education, and that he was more interested in his TV career than in grading tests. But Danza, 59, surprised them all.

"They saw me sweat. They saw me fail. They saw me do what they do," he says. By the end of the year Danza had won over even the school's nononsense principal. "She actually said to me, 'If you mess up, you're outta here,' " he recalls. Today she says she'd hire Danza for real. Though he's no longer teaching, Danza is still working to improve public education. In October he returned to Philadelphia with U.S. Secretary of Education Arne Duncan to promote the Obama administration's TEACH initiative, which seeks to attract talented instructors. He's also penning a book about his experience, titled I Would Like to apologize to Every Teacher I've Ever Had. "We all have a part in this," says the father of three. "My mother used to say every kid should have someone who is irrationally committed to their future. If you are relentless from the first day, the kids will understand that education is important."

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