Double check your bylaws. We'd also suggest you really use caution with this. It's great if there are advocacy groups popping up, but the PTO's role really should be in facilitating discussions rather than taking a stand on what could ultimately be a political issue.
Our school committee recently voted to close our school. However, the majority of our local community are opposed to this decision and several action groups have sprung up to help save the school. Is there any restriction in using PTO funds to buy yard signs supporting those groups/keeping school open?