I don't know whether this is a local thing but I have spent years correcting my children when they insisted on saying we was instead of we were. It drove me mad, they never heard it at home but it seemed every other child spoke that way.
Last week DS2 came home from school and said
"Mum, I feel your pain. Miss X insists on saying 'you was and we was' and she is an English teacher."
Success at last!