Wiltshire Police is appealing for a woman driver to come forward after she witnessed an altercation between two teenage girls on Redhouse Way.
The incident happened on Friday, January 13 at around 3.30pm.
The driver of a car blew her horn when she saw an assault taking place. She then stopped and spoke to one of the girls - the victim - to check she was alright before driving off.
PC Daniel Thomas said: "We would like to speak to the woman driver to help us with our enquiries.
"Also, we would like to speak to anyone who may have seen or heard anything suspicious in this area at this time.
"It would have been a busy area with lots of children and parents around as it was the end of the school day."
If you can help police with their enquiries call PC Daniel Thomas on 101 or anonymously, via Crimestoppers, on 0800 555 111. Contact can also be made via e-mail: firstname.lastname@example.org
A 16-year-old girl from Swindon was arrested on suspicion of ABH and released on conditional bail.