Susan, this sounds like a situation in which the advice of an attorney would be most helpful; not to sue the organization, but to review any formal agreements between you and them and to write letters reminding them of their obligations -- IF those were spelled out in a written agreement when you all got together. The attorney might also advise you about what to put in future agreements so you don't find yourself in a similar situation. Unfortunately, such situations happen too often. Finally, you might want to put the organization on notice that you will suspend your teaching efforts until the dispute is resolved. Again, an attorney's advice should be obtained before doing that. Thanks for your question and best wishes for a successful resolution.
