The assault on Courtney Rodgerson by a gang of youths took place in Penistone Road at about 3.35pm on Saturday, April 23.
Children and Young Persons Officers for the force identified four people involved through working with local schools.
They were interviewed on Tuesday, May 3 and have now all admitted their part in the offence.
Their details have now been passed to the Youth Offending Team.
PC Kevin Marsh, the investigating officer, said: “It was important that we quickly identified those involved in this despicable assault, and we were able to do so though working in partnership with schools.
“We continue to work with local schools to offer presentations and workshops in an effort to deter this kind of behaviour, and to hopefully educate young people and warn them of the potential consequences.
“Those who chose to stay and witness this particular assault will take part in a police led workshop on gang related violence and better citizenship, both in and outside of the school environment.
“Any kind of bullying or assault will not be tolerated under any circumstances, and I am positive that the ongoing work we do in schools can help to tackle these issues.
Courtney suffered minor injuries as a result of the incident but did not require hospital treatment.
If you have any information about the incident, please call 101 quoting incident number 686 of 23 April 2016.
Information can also be emailed to [email protected]