After being punched, stomped and kicked for nearly an hour by his own schoolmates, a semi-conscious 16-year-old boy was ordered to strip naked and lie in a crucifixion position on the ground, while his assailants jeered and took photographs.

The details of a vicious assault at a Nelson school which occurred last month, were released yesterday as the remaining accused admitted all charges in the Nelson Youth Court.

They say on the afternoon of May 5 a group of four students including the two accused, persuaded the victim, who was the same nationality, to go with them to another part of the school grounds.

One of the accused, referred in police notes as "A", grabbed the victim and threw him to the ground.

Straddling him about the chest he struck him multiple times with a closed fist to the head and face.

"A" stopped when he was pulled away from the victim by the principal assailant, identified as "B".

From that point "B" began a vicious and prolonged attack on the victim that continued over the following hour, police said.

The victim was unable get away from his assailants, and was totally submissive and unable to defend himself.

"B" began with multiple punches to the victim's head and face, before striking him with an elbow in the same areas.

As he grew tired of punching and elbow striking, he kicked and stomped on the victim's head and face.

At one point "B" pulled the victim off the ground by his hair, and kicked him about the head and face until the victim again fell to the ground.

He then dragged the victim over to a low wooden sign and draped his body over it, before beating him multiple times about the head and face with his fists and elbows.

"B" held the victim's arm out straight over the wooden sign and applied pressure, and used a twisting motion attempting to break his arm.

While the victim's head and body were draped over the wooden sign, "B" repeatedly stomped downwards with his feet, mainly aiming at the victim's head, as well as kicking him numerous times about the body.

On two occasions "B" placed lengths of timber about 50mm thick across the victim's shoulder and chest, and stomped on the wood until it broke.

At some stage during the assault the victim lost consciousness.

After about 60 minutes the semi-conscious victim was ordered into a submissive position, crouching on the ground with his head down and forehead on the ground, with his arms placed in front of his head on the ground.

Photographs were taken of the victim in this position.

"B" then struck the victim on his back numerous times with the broken pieces of timber.

The victim was then ordered to strip down to his underpants and lie crucifixion style on the ground.

Derogatory comments were directed at the victim by the group, and several more photographs were taken of him while he lay semi-clothed on the ground.

The victim was told to get dressed and was taken to a puddle of rainwater to wash the blood from his face.

"B" threatened the victim and the pair watching the assault that if they told anyone about what had happened they would get the same.

The victim then walked to where he knew he could get medical help and was taken to Nelson Hospital to receive medical attention for severe bruising, and lacerations and abrasions to his body.

Apart from his initial assault on the victim, "A" encouraged "B" in his actions and took photographs on his phone, while another student filmed five minutes of footage, and took several photographs, which have been viewed by police.

During the assault the pair took the victim's wallet containing $10 and his cash flow card.

In an attempt to try to placate both, the victim gave them his card pin number.

When spoken to by police the victim did not initially name his assailants for fear of a reprisal from them.

On Wednesday the two accused appeared in court on charges of injuring with intent to cause grievous bodily harm, aggravated robbery and kidnapping.

One admitted all charges on Wednesday, the other was given until yesterday to decide. He has also admitted them.

The two will appear in court again on June 22.