Colley Lane Primary School in Halesowen has sparked debate because of the ban, which has been introduced in a bid to raise standards of English for pupils.
Headteacher John White said he hoped the move would help children in their studies and future careers. Pupils are now banned from using phrases such as 'gonna', 'woz' or 'it wor me'.
The policy has been backed by Dudley North MP Ian Austin.
He said: "I am from the Black County and am very proud of the place I am from and my accent.
"But in the modern world when the job most youngsters get depends on their education, learning to present yourself properly is just as important as learning maths and English. No one should change their accent, but learning how to present your argument properly and having a good vocabulary is important."
But he insisted that he loves the regional accent, adding: "I have never changed my accent, I went to Russells Hall Primary and then, what is now, Castle High School."
It comes as more than 1,000 Express & Star readers took part in the debate by voting in an online poll. A total of 65 per cent said the dialect shouldn't be banned in the classroom, while 35 per cent said it should.
Councillor Tim Crumpton, cabinet member for education at Dudley Council, said: "I have no problem with teaching the children standard English in class, what I don't want is someone looking down their noses at our dialect – but, from what I can see, the school is trying to make sure the children understand good English."
At the school gate, the initative has received a mixed response. Ann Mills, aged 62, of Station Road in Old Hill, has two grandchildren at the school – a nine-year-old girl and seven-year-old boy.
She said: "I think in one way for the school it is a good idea, but at the same time it is about where these children live. You are going to speak the local dialect. I think we should be accepted for who we are. I'm proud of the way we speak."