Alison Forbes was sent home from Fairway primary last Wednesday, after a boy accused her of assaulting him. She has not been officially suspended but Mrs Forbes was advised by the local authority to work from home while it investigated the charges, made by the boy's parents.
Mrs Forbes has not been told who the boy is or even how old he is. The council would not discuss details of the case.
The National Association of Head Teachers is supporting her. John McNally, Birmingham NAHT council member, said: "She's distraught. Being head is the loneliest job in the world. You can feel very isolated.
"An accusation like this is one of the worst things that can happen to a head. It's worse than a bad inspection."
Alan Leech, NAHT west Midlands secretary, said complaints needed to be dealt with speedily. "Because of the nature of the job heads are quite high-profile people. If they are suddenly absent from work it leads to a lot of speculation."
This is not the first time Mrs Forbes has come under scrutiny. A petition from more than 30 parents was submitted to Birmingham council in 1998. The council took no action.
Mr McNally said: "Heads aren't in the job to be loved. When you take on a school you sometimes have to tread on people's toes."
Staff at Fairway would not comment on the allegations. A spokeswoman for Birmingham council said an inquiry was in progress.