I was a bit in the loop on a school in our district that just disbanded their PTA last month and are now a PTO. Boy, the PTA State leaders came in fighting to keep them on board, too. This local PTA unit felt that the State PTA leaders, in our state, were not serving them in ANY WAY. They felt the dues, which they sent more than $1,000 each year, would be better spent at their own school.
Their PTA bylaws required them to notify the State PTA that they wanted to end being a PTA; they had to allow State and/or National PTA representatives a chance to talk their membership out of disbanding their PTA, in a formal meeting. Which, got heated...and in the end made the PTA State/National people look ridiculous.
Once that was done and membership voted to disband their PTA and become a PTO, they had to pick a date that would work to move from the PTA nonprofit status to the PTO nonprofit status. You have to allow time to get the new nonprofit status set up, so that you can transfer all of your funds into your PTO account. Don't let anyone tell you that you have to donate the money away, or spend it down to a penny, or turn it in to the State PTA; you don't. But, you can donate it to your new PTO, as long as your new nonprofit status and bank account is open, make the transfer. Talk to an Accountant to make sure that you do this the correct way. That way you are covered. Also, you have to get a new Fed Tax ID number, which you can do on-line at no cost in about one minute. I highly recommend that you spend 5 minutes on the phone with an Accountant, they can tell you exactly what to do.
Disbanding can't be done overnight, because you really need to set up your PTO non-profit status and new bank account prior to totally disbanding. You might even run them both in tangent for a couple of weeks while all of the paperwork is being finalized by your state. The best advice is to talk with an accountant and an attorney over the phone for a little free advice. Maybe your school corporation is willing to help you work through the process. Our school corporation saw the need to help schools that were trying to go from PTA to PTO and had a local attorney, on our school board, step up and set up a nonprofit umbrella for all of our schools to sit under and operate as PTO's. Good Luck!