Earl J. Hart, 86, a revered math teacher for 52 years at St. Joseph's Preparatory School in courses ranging from algebra to computer science, died of heart failure Tuesday at Bryn Mawr Hospital. He lived in Rosemont.

Nearly 9,000 students studied under Mr. Hart, including many future lawyers, judges and doctors - and one mayor-to-be.

"Earl Hart was a very kind and focused man," said Mayor Nutter, a St. Joe's graduate. "I always enjoyed him in school."

Mr. Hart was born in West Philadelphia, the eldest of a carpenter's five children. For winning a spelling bee in grade school, he received two tickets to the Thanksgiving Day football game between St. Joe's and Roman Catholic at Shibe Park. It was his first football game and the first time he had heard of St. Joe's.

He went on to attend the school on a scholarship that covered half the $150 tuition. When he graduated in 1939, Mr. Hart dreamed of becoming a math teacher, but did not have money for college. He managed to attend St. Joseph's College on a partial work scholarship that required him to dig ditches between taking classes. He graduated with a bachelor's degree in mathematics in 1943.

Mr. Hart was refused induction into the Army during World War II because he had no left eye, having lost it in a firecracker accident when he was 5.

Instead, he worked in the ballistics lab at the Frankford Arsenal for a few months. He started teaching math at St. Joe's Prep in late 1943.

For the next 52 years, Mr. Hart taught every mathematics class in all four grades, starting with chalk and blackboards and advancing to computers.

For several years, St. Joe's teachers wore black robes. "That helped differentiate between young teachers and students," said Gus Kueny, a former student, teacher and vice president. "When I traveled all over the country for the Prep, one of the first questions asked of me by alums of all ages was, 'How is Mr. Hart?' He was one of those teachers they never forgot. He expected the most out of each student and stood for greatness."

Mr. Hart tired of his clothes being covered in chalk, so he began wearing a white lab coat to class. "I go through a lot of chalk," he told the Philadelphia Daily News in 1993. "I used to be a mess at the end of a day."

Mr. Hart married Elizabeth Rowland in 1943, and they raised a daughter in Southwest Philadelphia before moving to Penn Wynn in 1961. His wife died in 1969. Mr. Hart had lived with his daughter, Joanne Boylan, for the last 24 years.

"My father came home from teaching, took a nap, ate dinner, then taught night classes at St. Joseph's University for 35 years," said his daughter (who described herself as horrible at math). "He drove a succession of ugly used cars, from a bright-red Rambler to a big, blue Lincoln. He worked hard at two jobs making just peanuts in the early days. At first he did not even have health insurance."

Mr. Hart could have made more money in a different field, said grandson Kevin Boylan, a hedge-fund manager. "At one point, my grandfather wrote sonar manuals for RCA. He believed teaching young people had a more profound impact."

In 1986, the computer center at St. Joe's Prep was named in Mr. Hart's honor. In 1988, on his 45th anniversary as a teacher, St. Joseph's University gave him an honorary doctorate. From then on, he was Dr. Hart.

In addition to his daughter and grandson, Mr. Hart is survived by two more grandchildren; one great-grandchild; one brother; and two sisters.

Friends may call from 6 to 8 p.m. tomorrow at St. Joseph's Prep, 1733 W. Girard Ave., and after 9 a.m. Tuesday at the Church of the Gesu, 18th Street and Girard Avenue, where a Funeral Mass will be said at 11 a.m. Burial will be in Calvary Cemetery, West Conshohocken.

Memorial donations may be made to the Earl J. Hart Scholarship Fund, 1733 W. Girard Ave., Philadelphia 19130-1599.