A fight broke out between a group of 40 school children in Howard Davis Park at around 4 o'clock on Friday 14 June.
Many of them filmed in on their mobile phones and shared it on the social media site Snapchat.
One 15-year-old was assaulted, as well as a member of the public who intervened. No one was seriously injured but one boy was seen leaving with a "sizable amount of blood" on his white school shirt.
Police are asking parents to speak to their children about whether they are aware of or have any of the footage of the fight on their phones.
Anyone with information can contact police on 612612 or anonymously via Crimestoppers on 0800 555 111.