Thugs involved in an attack on Doncaster students, which was filmed on a mobile phone, are being hunted by the police.
A recording of the brutality has gone viral online after being published on the Scumhunter Doncaster page on Facebook and being shared thousands of times.
The shocking footage shows one youth in a school uniform on a field - believed to be in Hyde Park, Doncaster - initially trading punches with a bare-chested youth.
Footage shows the school boy retreating backwards while the bare chested youth advances.
A number of other youths are seen in the video watching the fight and encouraging the violence.
One can be heard shouting 'get it done' and others are heard saying 'make him pass out' and 'take him down'.
When the schoolboy reaches a fence and is unable to retreat any further he is attacked from behind by a second bare chested youth before falling to the ground and being set upon by a mob of thugs, a number of whom kick and stamp on him as he is down.
The mobile phone footage then shows a second youth in a school uniform motionless on the ground before he is kicked by one thug seconds before his head is stamped on by the bare-chested youth involved in the initial fight, who appears to be wearing a knuckle duster.
A South Yorkshire Police spokeswoman said: "Police have been made aware of a video circulating on social media of an altercation between what appears to be teenage boys.
"While the incident is believed to have taken place in Doncaster, there is no specific location and no date as to when it actually occurred.
"Officers are investigating and conducting numerous lines of enquiry to establish the circumstances, and following up various leads to be able to identify those involved
"Anyone who may have information in relation to the incident is asked to please come forward."
Anyone with information should call South Yorkshire Police on 101 or Crimestoppers on 0800 555111.