He believes school bullying -- whether online or in person -- is playing a huge part in the rates of youth suicide.
Only minutes before speaking to the Herald, a man approached him looking for advice after his 15-year-old daughter tried to kill herself.
"Unfortunately, the rate of suicide has gone up. Whereas girls in the past would have done more self-harm than suicide, I think (the rate) has gone up for girls as well," he told the Herald.
"Obviously bullying does play a part in it. I actually just spoke to a father, not 10 minutes ago, who looked for the phone number of (support group) Pieta House.
"He just walked up to me and goes 'sorry for disturbing you, you couldn't give me the phone number and details of Pieta House. My daughter tried to kill herself'," Mr Quinn said.
"Again it's down to school bullying," he added.
John has become involved in suicide awareness campaigns since Sean killed himself in 2005.
Although his son was not bullied, the Clondalkin father has come into contact with many teenagers who have suffered at the hands of schoolyard thugs.
He added: "If girls fight, they tend not to let it go. They keep it going. Unfortunately, school bullying does seem to be fairly high.
"School bullying is playing a huge part in the rates of suicide."
He knows of parents who approached schools about bullying and they felt not enough was being done.
"I'm not sure if the schools do take it seriously enough. What's the answer? Expel. There's no point in suspending somebody. You just expel the one that's perpetrating it," he insisted.
Mr Quinn strongly believes psychological is worse physical harassment and agreed "it mightn't do any harm" to increase garda powers to tackle the issue.
"If a young person is being harassed in school or in the workplace, it may not do no harm to go to the police, report it if you have proof and for them to act on it," he said.
Sean (17) took his own life in the family home in Quarryvale in July 2005 last year.