The term, "teacher collective," has no legal meaning. There is nothing in the California Corporations Code which permits an organization called a "collective." There is, however an "nonprofit association," so I'll assume that this is the true organizational structure.
An S Corporation cannot be a nonprofit entity, because profits in an S Corporation automatically pass through to its shareholders.
My point here is that the real question here is: who or what entity owns the assets of this organization (equipment, supplies, leases, intellectual property, enrollment lists, etc.)? And, in particular, who owns the name of the organization? These questions are not easily answered, except to the extent that a particular person may have filed a "statement of authority" for the collective/association with the county -- or registered a fictitious business name. Or, where a certificate of title is necessary to confirm ownership, or a signature on a lease.
Example: Let's say that this S Corp owner has the lease on the facility, and that her corporation owns the computer system with the student information, is the signatory of the business bank accounts. On that basis, the owner can usurp everyone else's authority and simply push anyone who disagrees out. It's the old saying, "The person with the gold, makes the rules."
Now, it's quite possible that the other members of this collective could file a lawsuit for a breach of covenant or fiduciary by the S Corp owner, and then try to prove that the S Corp owner had previously assigned her interests in the S Corp assets to the collective. But, that sort of fact-intensive lawsuit will cost a lot
of money. Unless everyone groups together, hires a lawyer and pushes back in a hurry, the S Corp owner may simply take over by fiat, assuming she controls the financial strings.
Frankly, the issue of the S Corp operating as a 501(c)(3) bothers me a great deal. I doubt that the IRS will permit this to continue for more than the current tax year. It may be that the parties involved simply don't understand the legal and tax issues, so the organization is malformed.
Regardless, if the goal is to prevent the S Corp owner from simply taking back the reins of power, the other teachers will need to either convince the parents to bring their money to a new legal organization created by those teachers -- because as long as the S Corp owner is collecting tuition, then she has de facto control of the school, unless and until a court orders otherwise.
For a civil litigation attorney referral, see this link
Hope this helps.