I looked it up the other day when it got mentioned as it felt ridiculously lenient but it seems to fit the sentencing guidance. That said, there were at least 4 aggravating issues that should be taken into account.
The crime itself is bad enough and up there with very serious assaults as the one having the biggest victim impact but when you add in the planning to lure the girls, use of weapons and, crucially for me, the videoing / sharing it to increase the victims’ humiliation it all feels ridiculously lenient. The fact they were prepared to film and share what they did shows a complete disregard for the law that appears to have been justified and the sentencing doesn’t said much of a message out to other teenage boys with misogynistic ideas.