I did not realise as a head in the debate leading up to going grant-maintained that it was theoretically possible for a majority of governors to become a hostile faction. It hasn't happened yet, but three of my co-optees already have the same kind of agenda and I can see how easy it would for spaces to be filled by others of the same ilk.
In our local authority the culture seems to me to be strongly anti "education establishment", and governors are encouraged to challenge us. There's nothing wrong in that, but I would like to think we started with a balance of interests as the law originally intended. Am I getting paranoid?
The law may have intended a balance of interests, but in the grant-maintained sector it was certainly a deliberate feature to make co-opted governors a permanent majority, and I don't think you are paranoid to recognise that there is a slight danger of a strong homogeneous group eventually establishing themselves.
The fact that co-opted governors in GM schools can vote in future co-options (which in local authority maintained schools they may not) does make it necessary for other groups to be slightly more vigilant.
I wouldn't exaggerate the danger, however. The parent and teacher governors of your own school, with you, have so much common ground and so much shared experience and commitment that there is more going for them than numbers alone.
The best advice I can give the "school" contingent is not to lie back and let co-options happen, but to have your eyes open always for suitable co-optees with valuable experience and commitment to the school and to be ready with names, so that there is always a good choice. Your greatest enemy is apathy in the school group.
It is also important that you have a system of governor involvement which is part of the governing body's expectation of all its members. Thus you will expose your co-opted governors to the reality of the school's life and work - very good for anybody with too many theories, and calculated to build a united governing body in which there is no more talk of "thee and me".