The boy, 15, was on a school trip with Donvale Christian College when he decided to squeeze through a crack in the boulder in what is commonly known among climbers as 'The Squeeze Test'.

Sgt Dale McIvor of Horsham said the boy's teacher alerted police at 6pm and he was later taken to Wimmera Base Hospital for treatment.

An Ambulance Victoria spokeswoman confirmed paramedics attended the scene, but the teenager was not injured.

Natimuk climber Gareth Llewellin said he also attended the scene and helped with the rescue efforts.

"If you are not a climber it's a strange thing to hear about, but the Squeeze Test is something that's commonly done," Mr Llewellin said.

"It's a vertical crack in a boulder under a cliff called Tiger Wall and it's too narrow to walk through, so you have to turn sideways and go through it with your body vertical."

Mr Llewellin said he went in after the teenager and helped lift him out because his hips were stuck.

"It was a bit cold and the paramedics were taking precautions," he said.

"I was talking to him and he was fine, although he was embarrassed, but we were all very relieved because we thought there had been a bad accident.

"Thankfully it was just something a bit strange ? more like a child getting their wrist in a drain in a bathroom."

State Emergency Service Midwest region duty officer John Hooper said the teenager was successfully removed from the boulder just after 7pm.

"Rescue crews manoeuvred him sideways and gave him a gentle lift and were able to pop him out," Mr Hooper said.

He said Horsham SES Unit and Arapiles Rescue Group members also attended the scene.