Most teachers these days last no more than five to 10 years in the classroom, but Paul Miller taught math for nearly 80. At one point, he was considered the "oldest active accredited teacher" in the U.S.

His career started in his hometown of Baltimore. It was 1934, the Dust Bowl was wreaking havoc in the Plains, Bonnie and Clyde were gunned down by police in Louisiana, and a thuggish politician named Adolf Hitler became president of Germany.

Miller taught elementary school kids by day, college students at night and his mother on weekends.

"I had to teach her how to write her name and the address of her house," he says.

His parents, Jewish immigrants from Lithuania, had very little schooling. They had arrived in the U.S. long before the Nazis occupied their country in 1941.

"My parents spoke Yiddish," says Miller. "They didn't know any English at all."

Miller didn't know English very well himself when he started grammar school. But he went on to do well and enrolled in the only college he could afford, a teachers school. It turned out to be a good decision because teaching was one of the few jobs available during the Great Depression. Every dollar Miller made as a teacher he gave to his parents — until he got married.

Miller and his wife raised seven children during some pretty tough times. The family struggled on his teacher wages, but Lisa, Miller's youngest child, remembers that as long as her dad was teaching, he was happy.

"I don't think he ever considered it work because he loved what he was doing," she says.

These days Miller, who has lost most of his hearing, stays in an assisted living facility in Baltimore where his family visits him often. His grandkids, Ilana and Max, call him "Papa." Miller loves playing poker with them, but he is hard to beat.

"Until I met Mr. Miller in 1978, I always thought math was boring," says one of his former students, John Shapiro. A computer engineer, Shapiro heard we were profiling his all-time favorite teacher and says he had to come by and explain why he liked Mr. Miller so much.

"He had a way of making it very easy, very simple," he says. "It worked for me, that's for sure."

Miller says he lights up when former students come by to see him, bringing back wonderful memories and reminding him of the impact he has had.

The key to teaching math, says Miller, boils down to one thing — repetition. "Repetition is one of the foundations of learning."

Repetition and rote memorization aren't exactly cutting edge these days, but it's hard to disagree with the advice Miller gives teachers who are just starting out: "Be sure that you know your subject."

You have to wonder though, is that enough? I remind Miller that even talented teachers who know their stuff are leaving the profession in droves these days. So I ask him whether in his 78-year career, there ever was a time he felt like leaving the profession.

"Any time you have a bad day you think of that," says Miller. "The next morning, it's all forgotten."

Miller chuckles. It's clear he still misses being in the classroom. Even a heart attack at age 84 didn't stop him from going back to teaching. Miller continued for 14 more years.

By the time he retired in 2014, he had written a college math textbook and become the first Maryland teacher to be inducted into the National Teachers Hall of Fame.

It was a long overdue recognition that Miller wasn't sure he deserved and certainly never expected.

"If you become a teacher to become famous, forget it," he says laughing.

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