A 13-year-old boy had to be taken home in the back of an ambulance this week after he spent a morning drinking rum in the back of a Horowhenua College classroom.

A teacher at the Levin school found him with a 750ml water bottle, used to conceal the liquor, on Monday morning.

He was taken to an administration office where he began vomiting and was disoriented, so an ambulance was called.

"He got worse. He was obviously ill, very lethargic, vomiting, not aware of his surroundings, very much in need of medical attention," principal Brenda Burns told The Dominion Post.

Ambulance officers checked the boy's vital signs, put him on a stretcher and took him home.

Another Year 9 pupil had supplied the boy with the liquor, believed to be from his home, Mrs Burns said.

She described it as a one-off incident.

"The child could have been asking for help. They tend to hide binge-drinking on the weekend but, during the week, they are not hiding it so there may be some other issue."

Capital and Coast District Health Board chief medical officer Geoff Robinson said the boy could have easily died.