He was a large, imposing figure and tough when he needed to be, but Jack Campbell didn't show it much.

As a math teacher to classrooms full of boys at St. Thomas Academy for nearly four decades, "Prof" Campbell, as they called him, instead led by example and connected with kids in a way not all teachers could, former students said.

Campbell died Saturday of heart and kidney failure. He was 94.

Campbell met his future wife, Iris McGraw, while they were both in seventh grade in Litchfield, Minn. He was salutatorian of their high school class; she was valedictorian, something she teased him about, his family said. A high school football coach encouraged Campbell to go to college and helped get him into St. Thomas. He married Iris in 1942, the year he began teaching at St. Thomas Academy in St. Paul.

He left the school for a couple of years to serve in the Navy as a radar tech during World War II. He also spent a couple of years trying the camping trailer business, but he came back to St. Thomas because he loved teaching and the school, friends and family members said. Faculty members at St. Thomas, many of whom also served in the war, were his social circle, now known as the "old guard."

Campbell was brilliant at math, and could explain it to students who weren't, said Gerry Brown, a former student who went on to become a teaching colleague at St. Thomas. "When someone can do that and they can turn on the light in the eyes of a student ... that's a great talent."

He and Iris raised four boys in their south Minneapolis home. He went to school early each day, coaching wrestling, track and football afterward, and grading homework at home at night. He found time to help students who needed extra attention, his son Jack Campbell said.

"We had kids that would come by our house ... and knock on the door and ask for help," his son said. "It always surprised me. I'd answer the door ... and I'd see a senior asking 'Is Prof Campbell home? Prof, can you help me with this?' He was extraordinarily patient."

Campbell tailored his actions to the situation, his son said. "If he had a football team that needed to be yelled at, he could do that. If he needed to put an arm around a kid who was struggling in algebra, he could do that."

He also had a sense of humor. Dan Forby remembered a sophomore algebra class in 1950: "Jack gave us a problem to solve. I spent years trying to figure it out until somebody told me: 'That's an insoluble problem.'

"A couple years ago I saw Jack at a reunion and told him I was still trying to solve that problem. He said, 'That's OK, I'll give you another five years.'"

After Campbell retired in 1983, he and Iris spent long summers at a family lake cabin in central Minnesota and volunteering together at the Church of St. Peter in Mendota, where they moved in 1975.

St. Thomas Academy awarded Campbell the 2011 Opus Sancti Thomae award and the Myser Family Teaching Excellence award.

Campbell was a fan of Louis L'Amour novels and John Wayne movies, his son said. The characters showed the kind of quiet strength he saw in his father.

Iris passed away in 2007, after 65 years of marriage. In addition to his son Jack, Campbell is survived by sons Patrick, Mike and Tim, 10 grandchildren and eight great-grandchildren.

Funeral mass will be at 10:30 a.m. Wednesday at the Church of St. Peter, 1405 Sibley Memorial Hwy., Mendota. Visitation is an hour before the mass.

Pam Louwagie • 612-673-7102