Advice please, physical violance

[debsl75]

I'm going to make this brief as otherwise I will become emotional and ramble.
Dd 13, had problems with a girl since year7 on and off. School made some attempt to deal with it but as it has continued for this long it would appear that it hasn't worked! Last week Dd had a quiet word with a girl in her form bully girl over hears and starts verbally abusing my Dd even though it has nothing to do with her. Dd returned the verbals, needless to say lots of nasty things said on both sides, alot of the class sided with bully girl (fear factor). One girl, new to the school (excluded from 2 previouse schools for physical violence) takes it upon herself to attempt to attack my dd but was held back by another girl. Dd went to head of year to report this attempt but nothing was done. At the next meeting in corridor(hour or so later) my dd wasn't so lucky and said girl grabbed her by her hair, pushed her against wall and attempted to break her fingers before 2 other girls broke it up. School failed to inform me and I knew nothing of it until dd came home. Went to speak to school next morning, appology for not calling, dd requested to move form but has been told that she can't go into the form with some girls she has made friends with (everyone eles runs a mile due to being associated with a bullied girl).
Question is, has the school failed in it's duty of care by allowing a known violent child to attack my dd especially as they had been warned she had threatened to do it? And as I feel this to be the case, should I press for her to be given what she wants as she has been the victim in all this? Basically should I use the lack of duty of care as a barganing tool to get her put with her friends?
This is abit more complicated then it may appear. Bully girl has a strange obsession with dd.
Violent girl perm. excluded from school but bully girl who started it remains un dealt with as usual.
Any help please?

[SlightlySuperiorPeasant]

Report it to the police. IME that's when it starts getting taken seriously.

I take it this is your DD's last year before GCSEs start? If so, I would seriously look at moving schools. This has been going on for 2 years. Enough.