That ridiculously low amount was a pure political ploy that was designed to guarantee Martinez would turn it down. Then the public would be upset and call Martinez "greedy" when it was the BOARD that was entirely at fault.
Yes, it's going to cost money, mostly likely covered by the district's insurance carriers, but the right to due process, including the right to sue, is part of the American legal system. Martinez's rights were trampled upon. There is no question of it.
25K is absolutely nothing. Martinez should get many times that amount. The board not only breached his contract, they also defamed him.