The geography teacher at St Nathy's College, Ballaghdereen, Co Roscommon, is also manager of the Galway football team. He can't remember a time when he wasn't interested in sport.
As a schoolboy, John O'Mahony played for St Nathy's where he was a boarder. Later, he played Gaelic football for Mayo and for his local club in Ballaghdereen. A graduate of St Patrick's College, Maynooth, with a HDip from UCG, O'Mahony won an under-21, All-Ireland medal during his first year teaching, back at St Nathy's. He represented Mayo for three years at senior level, before opting to concentrate on coaching and management.
"Coming back to St Nathy's allowed me to continue my interest and involvement in football management," he explains. "I've been helped by the fact that I have time, particularly during the summer, to do the job."
O'Mahony has a strong record of success. He began by coaching and managing the under-21 Mayo team and lead them to victory in the 1983 All-Ireland final. Between 1988 and 1991, he coached and managed the senior Mayo team. During this period, they won two Connacht championships and qualified for their first all-Ireland senior final in 38 years.
He took a year out, and then went to coach and manage the Leitrim team in 1993. The following year, they won their first Connacht championship in 67 years. After a four-year stint with Leitrim, he moved to Galway, which won the All-Ireland final last year.
What, then, is the secret of his success? Teamwork, he says, emphatically. "Getting people to work together to achieve a goal is the key."
And the future? "We'll see," he says. "It's becoming increasingly demanding to combine what is essentially two full-time roles. At this time of the year - the busiest - I'm teaching from 9 a.m. to 4 p.m. and then I'm gone every evening to training, coaching and meetings." It's particularly demanding of family life.
"I couldn't do it without an understanding family," he stresses. "Fortunately, my wife, Gerardine, is very interested in sport and plays a very supportive role." All of his five daughters, too, are "sports fanatics."
The Galway manager's sporting interests are not confined to county level, however. He is also closely involved with football at school. When we spoke, he had just watched St Nathy's qualify for the Connacht Junior Finals. "Working with children is more enjoyable, he admits. "There's less pressure and you're not in the public eye."
For O'Mahony, involvement in sport is a great reliever of stress. School is more pressured now than in the past, for everyone - students, staff and parents, he says. "It's important to get a correct balance: you can't concentrate exclusively on the academic.
"Students can't sit in class between 9 a.m. to 4 p.m. and then study for four or five hours every night between September and June. They need an outlet, and games help to give them more quality study."
When it comes to sport and recreation in schools, government policy is somewhat lacking, he says. When St Nathy's, a former all-boys school, was amalgamated with two other local schools and became co-ed, the Department put funds into the academic facilities, but few grants were available to fund sports facilities.
"We found we had to do a lot of fund-raising ourselves," says O'Mahony.