I'm going to guess that you have not been there. You really should visit before you decide.
I used to teach at the High School, so I can probably answer any questions you have. Window Rock Unified HS is on the Navajo Reservation. Obviously almost all of the kids are Navajo. A majority of the skilled professionals, like teachers are not.
The Rez is the Third World. Most people from the East Coast are amazed when they visit the Rez. A common comment is "I didn't know people lived like this".
Some tips:
1) If you live there you will almost have to accept the housing the school provides, otherwise you will need to commute from Gallup NM. If you accept housing insist on an appartment, do not accept a trailer. You're much less likely to be robbed that way.
2) Count on having you home robbed. It might not happen, but when it does you'll much better off if you are prepare.
3) If you are not Navajo, you will have no protection from the police or the courts. That is unless your raped or murdered. Major cirmes are investigated by the FBI.
4) The Rez is Soveregn (sp). The State of Arizona (or New Mexico) will not help you. You can't file a civil case in state courts, they don't have juridiction.
5) Contracts are one sided. They will serve to bind you only. Any attemps that you make to have the school enforce the contract will be ignored.
6) Driving at night is very dangerous. Assume everyone is drunk, and that a cow will be standing in the road as you crest the hill. Everyone hits a cow eventually. It's open range and there are no fences.
7) About one person in 10 that is new to the Rez disappears after they see what they have gotten themselves into. They don't bother to resign, they just go away.
6) If you're not used to the environment you will likely get sick - usually a severe flu/cold. There is basically no medical care. Sage Memorial in Ganado is a private hospital that was highly recommend, but never had the priviledge to visit. DO NOT GO TO AN INS CLINIC/HOPITAL.
8) Don't have any expectations.
Some additional sources of info:
http://azcentral.greatschools.net/modperl/go/AZ
www.navajotimes.com
Sorry to be so negative. Some folks love the Rez - but often these are social misfits. I'll be happy to answer any questions so please ask.