Well, first off, for a good answer on a Roberts Rules question, try
www.RobertsRules.com.
But is this correct? It probably is correct in that the bylaws of the organization fix the procedures for establishing the board, and simply choosing to ignore them in the name of expedience and "getting along" is a first step down a slippery slope. And if it is necessary to oust an elected officer in order to allow for election from a new pool of candidates, which one do you choose as the sacrificial lamb? I'm not saying you don't have a valid issue, but try to imagine yourself in their positions.
But there are ways around these problems. Approach them creatively, not confrontationally. Is there allowance for officers to co-share a position? Would it be possible for a newcomer to be placed into a co-vice-president office, for example? The vice-president responsible for fund raising may be especially interested in this idea.
Our district merged two schools a few years back. Those schools worked hard to facilitate a merger of the PTAs, and by all accounts it worked pretty well.
However, it appears your case is more one needing to assimilate newcomers into an existing school because of closure. We have that this year, as the next school over was closed and the population reassigned to two other schools. I appreciate that they loved their school and worked hard to make it a good one. But we've been here for 35 years, and have worked hard to make our school a good one. Welcome to our school, but it is still our school, and not the result of a merger.
Does that mean their parent leadership is out of the loop? Well, it apparently does to some of our parents, but I'm trying to avoid it.
Last spring our hands were tied with respect to electing executive officers. There was a spirited effort to block closure at the ballot box. Our bylaws and meeting schedules were going to result in officer elections before the final resolution of the closure issue. It would have been wildly inappropriate for us to recruit officers from their membership at that point. And what if we did and the vote succeeded in keeping them open?
But after the vote, I asked my counterpart to co-chair my committee. Then, when I was asked to fill the presidential vacancy created by resignation, I sought out a co-president from the other school population. This also left my co-chair all alone to run the committee. I've also looked first to that group to fill any additional board vacancies that may arise.
You really can't force them to accept you with open arms. All you can do is make sure they know you are available and ready to help. And if all else fails, remember this: they can't elect next year's officers without taking nominations from the floor.
Good luck.