I agree with HW Wong (Disunity: Gov't policies to blame, not vernacular schools) that the main cause of racial disunity is not vernacular schools alone. Introducing English-medium schools alone will not create racial unity overnight by itself. Racial unity does not fall from the sky into our concrete structured buildings called "schools".
There must be first a willingness and then the will to bring about racial unity. There are many "up there" who do not want racial unity as they exist and thrive on racial disunity.