I was at a Mark Abrams training Friday and during the break asked him about the town meeting vote necessary if an alternative to the statutory formula is used. Having taken a basic school spending workshop from him earlier, I came away with the understanding that a unanimous vote was required. Mark confirmed that a unanimous vote is needed, always has been.
He recalled that he was contacted by Andy Churchill three years ago about helping the schools develop an alternative assessment methodology -- he indicated he was willing but the school committee never got back to him. Apparently they chose to create their own.
FWIW, the school spending training was attended by an Amherst staff person.