Mediocrity is a terrible standard to apply when hiring and retaining teachers. Plenty of research has proven the importance of effective teaching in promoting student emotional, social, and intellectual achievement.
A friend for whom I worked talked about the "EIEIO Rule" when recruiting new faculty and considering renewals of veteran teachers' contracts. These are the qualities I suggest we look for when building a dynamic and successful school:
I- Interpersonal Skills
O- Ongoing Learning