I'm sorry you had that negative experience.
A PTO can be anything from an informal committe-like extension of the school that is totally controlled by the principal to a fully independent 501(c)(3) tax exempt organization set up as a qualified charitable organization.
While there are common practices many of us share, PTOs are are not affilated with any national/state group and there are no set "rules" and no governing authority. Most of us would expect to operate with bylaws, annual elections, and basic parliamentary procedure at meetings. But there's nothing to say a PTO must do those things.
It's a long shot, but you can check with your school district to see if they have any district level policies on how a parent group should be run.
In a situation like yours, change usually occurs because:
- Parents interested in change become active in the organization and help it evolve slowly over time;
- Parents who feel strongly enough band together to agressively voice their concerns regarding how things are run, basically forcing change;
- The school gets a new principal or some new administrative guidance affords an opportunity to start fresh.
Or...it just continues on as is.
So, yes, a coup is possible. Will it work/be effective? No guarantees.
Good luck.