This is a policy fraught with disaster. I know of a head of department who gives people he dislikes poor classes how will they fare? What of classes that may be streamed into ability groups? This is a policy that potentially marginalises the poor or weaker student, that creates a have and have not with teachers. It does not encourage good teaching and sets a tone of failure and underachievement.
It will also act to ensure that lower decile schools struggle to attract and retain good teachers, accentuating the problem and amplifying the failure.

Andrew