See Hirhurim's discussion at http://torahmusings.com/2013/01/kosher-severance/
My comment in response to several of the comments there:
Chodesh l'shanah is the only protection that a Rebbe has against a system that underpays him (ask me offline if you need that confirmed), and can and does demote him, cut his paycheck and/or discharge him without due process. Just as a kesubah was instituted as a check on divorce, chodesh l'shanah serves as a check on the whim, caprice or malevolence of a supervisor, administrator or significant other. Our system is very different from the public school system. Rabbeim are not unionized, have no grievance procedures, and no ombudsmen.
It is shameful that YU's University-School Partnership advises schools to preclude chodesh l'shanah in their contracts. This is simply exploitation. I am sure they did not consult the Roshei Yeshiva as to the advisability of this maneuver - much less Ba'alei Mussar. The ethical lapse is extraordinary. What happened - if nothing else - to v'asita ha'yashar v'ha'tov?!