A 16-year-old needed reconstructive surgery after his thumb was left hanging by a tiny piece of skin.
The boy's mum claims her son's attacker tried to kill him during a fight outside Hamilton's Fraser High School on Friday afternoon.
"There was an altercation and this kid actually tried to kill him," Pauline Hania said. "He tried to get him in the stomach, my son has cuts on his shorts from the knife," she said.
Her son needed four hours of reconstructive surgery.
She had initially been displeased with the response from the school, but today told the Herald they had been "more helpful" yesterday.