Good advice from the others. Firm but polite is certainly the best way.
If you don''t get anywhere, you need to go to the deputy head responsible for that area of the school, and if that fails, to the governing body. Find out who the parent governors are and speak to them. Senior management and governors are more likely to be able to do something than either the local authority or OFSTED. If you have to go to senior management, put your complaint in writing. If nothing happens, write again and copy to the Chair of Governors.
It''s also worth considering standing as a parent governor yourself, as a long-term strategy. My own experience is that this can be useful in lots of ways. First, the senior staff know you. Second, they know you can escalate things quite quickly. Both make them more likely to take your views seriously.
Also, if you now have Truancy Officer intervention, however unnecessarily, tell them what is going on.
My experience tells me there''s nothing scarier for a school than bad press. Considering the numerous high profile anti bullying campaigns that are going on with sports stars etc, I''d get in touch with a local paper and at least look into who''d be responsible for writing a piece on how the local schools deal with the problem (or fail to do so in this case).
Of course it wouldn''t be your opener but if you''re getting nowhere with the dragon you can at least mention you''ve been in touch with a journalist who is interested in the matter.
Better to come armed and prepared.