Seven-year-old Charley Daniel told teachers her right arm was hurting her after she fell over in assembly but claims she was told to 'stop whining'.
She then had to write with the injured arm before her mother collected her at the end of the school day.
Charley's furious mum Natalie, 28, says she could see her daughter was hurt the moment she picked her up. She took her straight to hospital.
'I took her straight to A&E for an X-ray and they said straight away it was broken. I was fuming. All it would have taken was one phone call from the school to tell me she had an accident and I could have taken her to the hospital.
'It is heart-breaking that she was left on her own and in pain for the whole day. When I went to pick her up I could see she was struggling by the way she was holding her arm across her chest. She told me that when she complained about it she was told to 'stop whining'.'
Charley now has her arm in a cast and a sling. She says she repeatedly told her teachers at St Barnabas Primary School, Worcester, that her wrist was hurting, but they would not phone her mum and made her carry on with her lessons.
Natalie now says she will not let Charley return to the school in September:
'I have spoken to the headteacher. She didn't seem very sympathetic about it at all.
Charley is very upset and has told me she doesn't want to go back to that school and I don't blame her.'
The school's head Angela Deacon denied the school was at fault, saying:
'I have investigated the matter in school. She was seen by a first aider and ice was applied to the injury. She was revisited several times. It wasn't until the end of the day that she complained her wrist was hurting so she was told to make sure she told her mum about it.'