Legal right for separate meeting with headteacher?

I have repeatedly asked for separate meetings about my child with the headteacher, as I do not want to be in the same meetings as my abusive ex-wife. My child has written to the head to support my requests. The head has refused to meet me separately for 4 months. My son had been ideating suicide because he has been bullied at school. I have complained to the governors formally but they have upheld the head''s attempts to "broker" meetings including my ex (something I explicitly told him I didn''t want, in order that the meetings could be productive). The governors say I have no right of appeal other than to go to Ofsted or the Regional Schools Commission.

The head has said that the local authority has told him that it is in the child''s best interests that both parents are present in meetings, even when one parent has abused the other. The local authority has confirmed in writing to me that they are 100% confident that no one at the local authority would have given that advice.

The behaviour and decisions of the head and school governors are in direct contrast to the school that my child has now chosen to join - they were immediately supportive of separate meetings and did not ask any details why.

I have 2 children remaining at the school so I want to be able to cite my legal rights in detail for separate meetings.