Edward Bryan, 59, continued to deny any wrongdoing as he was sentenced, the Irish Independent reported. He was convicted last month in his third trial.
Bryan taught at the North Monastery School in Cork, where he also coached basketball and was briefly principal of the school. Three former students, now in their 40s, said Bryan molested them between 1987 and 1990 during periods when he gave them individual basketball coaching.
Judge Sean O'Donnabhain said at the hearing in Cork Circuit Criminal Court that Bryan had taken no responsibility for his actions and shown no remorse.
The victims said going through the three trials and repeated cross-examination was hard.
"I was never the guilty one. I had nothing to hide," one said. "I just wanted to be believed, to be vindicated, and I was."
Bryan's lawyers said they will probably appeal.