At St. Francis High School in La Canada, California, math teacher Jim O'Connor is known for his tough, no-nonsense approaching to algebra, pushing his students—all boys—into shape. O'Connor, a Vietnam vet told CBS News, "It drives me crazy when people say school should be fun. I mean, it's nice if it could be, but you can't make school fun."

Pat McGoldrick, a senior at St. Francis says, "[Until people get used to him,] they think he's really mean." But that all changed for Pat and his classmates when they visited Los Angeles Children's Hospital to recruit blood donors for a blood drive they were organizing. When the boys mentioned where they went to school, they were immediately met with awe. The hospital staff said things like, "Oh, so you must know Jim O'Connor. Isn't he wonderful?"

The boys were stunned and, if they were being honest, a little confused about the man they thought they knew. That confusion was cleared up when they saw a plaque in the hospital for all-time donors. At the top of the list? Jim O'Connor. A universal blood donor (type O-negative), O'Connor has donated a total of 72 gallons of blood and platelets since 1989, surely saving countless lives along the way.

But there was more that the boys learned that day: Jim O'Connor, who never married or had children of his own, volunteers three days a week holding and rocking sick and dying babies when their parents can't be there. O'Connor says of the babies, "I don't want to see them alone. You can't do that." O'Connor's students were blown away. "I've always respected him," says Pat, "but now it's to an even different degree—really to the point where I try to emulate him."