I joined the association when I first became a teacher because it was the right thing to do. They are the sole bargaining unit for us, and they had negotiated a pretty good contract. I felt it was my duty to say thanks by joining. Otherwise, I would kind of be a freeloader. Now, six years later, I am more involved and have become an officer of the association. I strongly believe in labor unions in general, and believe the protection they provide us is well worth the expense.
It is my opinion that not joining the association is not Mustachian, but it is cheap. Many people don't join because of political reasons, since the national association supports almost entirely Democratic candidates. But on the local level, the association really is there to serve the teachers' best interests. While I don't agree with everything the national or even state level association does, I whole-heartedly support my local.