The headmaster of the Sydney private school King's has backed away from his defence of a controversial sheep-tackling exercise involving students, saying he is "appalled" by the incident.

The ABC obtained video of the school's first and second XVs running into a sheep paddock, crash-tackling young rams and dragging them around by their feet at a farm in Orange last month.

The state's farming association described the incident as dangerous, "plain stupid" and "unacceptable".

In a statement to the media, headmaster Tim Hawkes said it was totally inappropriate.

"Frankly, I was appalled at the decision taken to allow the training exercise involving the sheep to take place," he said.

"Regardless of whether it was supervised, or that no animals or boys were harmed, it was totally inappropriate."

His remarks represent a backflip on his position when first approached by the ABC earlier this week.

The footage was taken on a farm in central NSW. ( 7:30 )

"The two rugby coaches involved were assured by the farmer beforehand that the activity was safe and all the more so because he would be supervising it carefully," Dr Hawkes said at the time.

"I am satisfied that the activity was properly supervised and that no animals or boys were hurt."

But earlier today, he contacted King's parents describing the exercise as a "poor choice".

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"Although training was given beforehand on how to handle sheep and the event was supervised by several experienced farmers, there was always the capacity for hurt," he wrote.

However, he did tell parents that the controversy raised issues about "whether an urbanised community understands rural ways and what the acceptable limits to media reporting should be".

Vets and farming groups have condemned the actions in the video. ( 7.30 )

Dr Hawkes has since spoken with New South Wales Farmers Association president Derek Schoen.

"The central issue is that respect that needs to be given to animals. It is vital that a culture of care and respect be engendered in all who live or work with animals," Dr Hawkes said.

Mr Schoen added: "My main concern is for the welfare of the boys and the animals they were working with.

"I am thankful that the no one was hurt and that no sheep suffered long-term injury.

"Clearly the animals were distressed and this has been a lesson for all those involved."