Barrister I think your wrong!
We tell children not to touch hot things when they're little,not to run across roads,to be kind,say please and thank you,to help one another ect.
Being a parent is about teaching your child/children lessons that will not only keep them safe,but that will hopefully help them to grow up to be happy,healthy,kind and loving well rounded adults.
All lessons we learn as a child may not seem fair at the time,but they do help us to grow into the adults that we want to become.
This may be just the thing that will make the boys teachers sit up and listen,maybe then they'll start dealing with the boys negative behavior towards others because from what the OP has said it doesn't sound like anything has been done in the past 5 years regarding the 3 boys behavior.
Also it might just make the parents think about the way they're parenting.They will have to sit up,take notice and take action!
I've witnessed this multiple times with children as young as 4 right up to older teenagers(I've taught children of all ages and needs for years)and honestly I've seen a real difference in a lot of the children that weren't involved in something because of they're behavior and they're parents and the support and strategies the teachers put in place.
With a lot of the children it had a really positive outcome with they're behavior.Lots of them a year later they'd become friends with the child/children they'd bullied previously and were being invited on play dates and party's.