You obviously do not understand. This shas nothing to do with moving teachers. It only has to do with 2 things. First, that black teachers have been historically more affected by budget cuts and reductions than white teachers. Second, the contract now says that seniority is not the only factor that can determine who is cut. They are allowed to factor teacher diversity of the entire district.
If I wanted to make a straw man argument, precedent aside and if you are taking performance out of the equation, why is seniority a better factor than diversity? Again, taking performance out, what makes tenure more favorable than diversity whether it be black, white, male , female, able bodied, disabled, veteran, non-veteran etc....?