Lunchtime Supervisors and Special Needs Child?

My daughter has a diagnosis of Asperger syndrome and other behavioural issues. She goes to a mainstream primary school and is very bright. She does not like to socialise and also eats very little. She has come home from school today really upset because the senior supervisor at lunchtime has forced her to eat all her dinner and shouted at her, this is not the first time this has happened. I am going to go into school and complain about this woman tomorrow but I don't want school to fob me off. What would be the best way to go about complaining?