Firstly, so sorry to hear your story. I would be fuming - it sounds like it's just been going on far too long and i cannot believe so little has been done about it. I would keep a detailed record of all incidents as described by your daughter. Back-date if possible. Then follow the steps below suggested by parentlineplus.org.uk
Key steps to follow when your child is bullied at school:
Check that the school has an anti-bullying policy and that procedures are being followed.
Contact the Head and ask for a meeting to discuss what can be done.
If you are not satisfied, write a letter of complaint to the head of the school. (Try the Children's Legal Centre or Advisory Centre for Education for help with this.)
If you are still not satisfied write to the Chair of Governors with a copy of the letter of complaint. Let them know your concerns and what you would like to be done.
And if you feel none of this resolves the situation you can write to the Director of Education at your Local Authority.
Lastly, complain to the Secretary of State for Education and Employment.
For more information on dealing with schools and bullying visit the ParentsCentre.
In the meantime, your daughter will need every opportunity to try to build her confidence and to understand that it's not her fault. I think, overall, that it is not especially helpful to keep her off school and you could run into trouble doing so.
Hope this helps and i really hope you get this sorted soon.