@IsabellaLinton
I've been sitting here thinking and imagining what Mon to Fri must be like for your daughter.
Firstly, there are a number of faux-naives on this thread as well who pretend that it is not so, it cant be, they've never heard of such a thing, they've checked their Koran, etc etc. As I tried to explain to others here, a non-muslim is seen as Kuffar (dirty).
This is what I suggest you do, in a formal way on paper, not email. You write to the Head Teacher, and do a b.c. to the Board of Governors and the Chief Superintendent of your local police. THIS IS A HATE CRIME. The school will not help you, because they have been instructed not to rock the boat. In the meantime, report this as a hate crime to the police.
Remember - If it were the other way around, a bunch of non-muslims were stopping one muslim kid sharing their table, her parents would be beating down the door at the Dept of Education.
What does the school say when you point out that you dd is ostracized?