Garrigan's parents enrolled him in the Helen Jordan Stage School to help the future pop star develop self-confidence.
"I was so shy and anxious as a kid that I remember, when I was about 11, walking to school and I'd cross the road if I saw anyone I knew coming towards me on the same side," says Steve.
"Interacting with people made me nervous so I'd try to avoid them as much as possible."
Steve, who reveals his anxiety issues in a new autobiography, High Hopes, co-written with
Sunday World journalist Neil Fetherstonhaugh, said his parents were banking on the stage school taking him and his sister, Fiona, "out of our shell."
"They enrolled us in the Helen Jordan Stage School, which at the time was in the basement of Findlater's Church on Parnell Square. I remember walking in the first time and there were all these loud kids there, singing and dancing. I just gave my name and immediately sat down quickly at the back and didn't say anything to anyone.
"I'd go there with Fiona every Wednesday evening. There were dance classes and there was acting and singing, but it took me weeks before I got involved in any of the activities. I'd just sit and watch while all the other kids were going through their routine. But I kept going every week because I knew, deep down, that if I ever got the opportunity to sing I could show them what I could do."
Although Steve had no ambition to become an actor, he eventually went on to land parts, including as an extra in Fair City. "It was through the stage school and some of the boys were picked to be part of a football team and I was one of them. I remember going into RTÉ for the very first time and going into the canteen, somewhere I've been many times since, and sitting down and getting free lunch. It was pretty exciting."
That lead to getting a part in the movie Agnes Brown. "That's really when the stage school did start helping me to come out of my shell," he adds.
Jordan, who was herself a child star with Maureen Potter in the Gaiety Theatre, and a showband singer with The Big Eight, says she enjoys making dreams come true for talented performers.
"I can actually recognise potential within five minutes of meeting a child," Helen says.
Currently one of the stars of the hit movie comedy Deep Cuts with Angeline Ball, Jordan recalls that Garrigan was "a quiet, shy youngster" when he first joined her school.
"I've seen lots of shy kids come in and blossom and you see them giving it socks on stage," she says. "Stage school is absolutely brilliant for helping children to bring out their personalities and build confidence through performance. I always felt that I had a gift for nurturing talent in young people, guiding and bringing that talent out.
"I'm very proud of all my students down through the years. I would highly recommend performing arts to parents of kids. Even if they don't go on to make a career out of it, it is so good for their social skills."
Several of Helen's former pupils are this year starring in some of Ireland's top Christmas pantos.
"Three of my students, Johnny Ward, who also now teaches in the school, Paul Ryder and Emma Warren are starring in the Aladdin panto with Alan Hughes in the National Stadium," she says.
"Fair City actor Ryan Andrews and his fiancée, Michaela O'Neill, who first met at my school as young students, have leading roles in Olly, Polly & The Beanstalk at the 3Olympia.
"I'm also delighted to showcase some of the school's current students who will feature in the Aladdin-themed Christmas event in Malahide Castle."