The 17-year-old fifth-year student was joking around with some friends on the way back from lunch when another boy suddenly "jerked his scrotum," the Irish Mirror reports.
A teacher and another student performed CPR on the victim before emergency medical services arrived. The injured boy was transported to an intensive care ward, where he was listed as in stable condition Friday night.
Gardai—the Irish police—have launched an investigation into the ball-squeezing incident, although witnesses say it was not malicious. The area was initially cordoned off as police treated the case as an assault.