www.sunderlandecho.com/news/crime/teenager-had-sex-with-13-year-old-girl-at-party-then-posted-pictures-of-it-online-1-6626838
Basically it seems to come down to the fact they took and posted photos on social media.
The boy who had sex with her got 9 months, the other two who got what is presumed to be blowjobs/handjobs got 12-month referral orders.