Instruction in formal grammar helps to open a world of possibilities to students who would otherwise be ostracized because they would be seen as unintelligent and incapable of learning. By teaching all students to become proficient in formal grammar we are able to give students an even playing field upon which they can enter society.
However, having said that, we as teachers should not look down upon students that choose to use non-standard English. In the homes and communities that make up society today, formal grammar usage is an exception not the law. It is in these close nit arenas that non-standard grammar is used not only as a way of communication, but as a way of "fitting in.aE