Rain, who turned 15 a week ago, put Kaleb into the recovery position and cleared his airway when Kaleb began frothing at the mouth.
"It kept coming, so I was wiping it away."
Rain called an ambulance, then Kaleb's father Marcus Duffy.
Rain said his actions were the result of picking up "bits and pieces" from Shortland Street, as well as health class.
Kaleb suffered a head injury and was rushed to Tauranga Hospital in a serious condition.
Mr Duffy said he had no idea how bad Kaleb's situation was until he saw him fighting staff at hospital - an effect of his injury.
"They were trying to hook him up with wires and stick needles into him and he was putting up quite a fight. They asked me if I could try to calm him," Mr Duffy said.
"He had no idea who I was, which just ripped my heart out.
"It had me and my three mates in tears for quite a while. There we were, three grown men bawling their eyes out."
Kaleb spent the night in an induced coma but woke 12 hours later and was walking around "being a smart arse". Two days later he was discharged.
Ten days on from being hit, Kaleb had his first day back at school yesterday.
"I feel good, I don't really feel anything really from it. I feel normal, feel all right," he said.