I have two boys - I am friends with all of their friends - as young as 4 years old kid. I want to know who my kids are hanging out with - "Sangat le bigarcha" - it is very true. One thing that worked for me is I am always doing school work with my kids like chaperon, substitute teacher, and even sports instructor etc. I am very involved with my kids activities - they are almost like my friends. I usually pick the toughest and bad boy of the class and befriend him and introduce my kids - that seems to be working so far.
I feel sorry for that kid and I was his parents I would go talk to the boys that are bullying them and talk to them like DINDUKHI mentioned - call them and have a party.
I pray for that kid - feels like its happening to my own kid.