The teachers were already able to give points and take points.  In fact, one of the characterizing events that helped develop Snape the bookswas the fact that he seemed partial to Slytherin and took points "unfairly" from Gryfindor.<br/><br/>It is likely expected that while teachers have a preferred House and want their House to win, that they display the professionalism and discipline of an adult and remain as impartial as possible.<br/><br/>But I think the precedent for this has already been set in canon.