Dear Jenny Wren
I have been where you are now, and my son where yours is. My guess is your ds is a sensitive boy and he has gone from a mixed primary to an all boys grammar. There is a massive power struggle in many boys grammars in y7 with boys vying to be the coolest, strongest etc. Often it seems some poor unwitting soul becomes the "victim" who other can score points off.
This is bullying. Don't let anyone tell you it isn't. The boys doing the things are bullies, and the bystanders who stand and watch and don't intervene, or more probably laugh make things much worse for your son. He really will feel noone likes him.
Write everything down. However trivial. These are the things we had - "borrowing" of a pe bag - which then turns up behind the shower
underhand comments in class, constantly being told he was a loser, and no one liked him, laughed at, pushed in the playground. The school did not want to listen unless it was physical violence, and said my ds needed to "toughen up".
Ask to see or at least speak to your son's teacher. Write down everything that he says happens to him and date and diary it. The send it all in IN WRITING to the school. Ask to see a copy of the school's antibullying policy. Individual acts may seem trivial, but when put together it is more obvious that it is bullying.
It is not up to your son to say what he wants to happen. It is up to the school to ensure he is happy and safe. EVERY CHILD MATTERS is the educational buzz phrase at the moment. Every child, however sensitive, has the right to be happy and safe in school.
From my own experience putting everything in writing to the school made things happen. Suddenly senior teachers became involved. If there is a trail of paper then the school know you could go back to this if ever you needed to take a complaint to the LEA.
I can also recommend Kidscape for information (the only registered antibullying charity in this country).
Good luck. There is light at the end of the tunnel. My ds is a confident happy boy now, and his "bullies" are now his friends. He is tougher as a result. But .... he wouldn't have got through it without some teacher intervention in the early days.
Your son can help matters my not showing that he is getting upset by it all. Encourage him to join clubs at lunchtime, preferably with boys from other classes. Try to find an older boy to befriend him on the train. Invite someone to the cinema and pizza or whatever is local to you and considered COOL. If your son can just turn a couple of boys in his form around, so they don't join in it will really help.