HUGE RED FLAG!!! I'm going to be harsh here, but if that were the attitude of my PTO, I would tell that they get $0 of my money from now on. Ok, now I'll calm down. CrewChief's advice about an audit is right on. That's good common sense for every group, even ones with stellar financial practices.
The money doens't belong to your treasurer or your president. It belongs to the members. As a member, you have the right to receive and your treasurer has the responsibilty to produce a written/printed accounting of AT LEAST the transactions for the year against your group's bank account. If that means your treasurer photocopies every page in the check register for the year because that's all the documentation she has at this point, so be it. I wonder, how does the Exec Board know there's enough money in the account to pay for those expenditures you vote on? Is it just first come, first served on expeditures? No planning!? Sigh.
Why do officers think they are not accountable to the members....which essentially means they are not accountable to the students. Your PTO may be run by the most wonderful, most sincere, most dedicated, most honest volunteers in the world, but this uninformed attitude about the financial records makes them look like they're trying to hide something. I hope for your group's sake that it's just ignorance, not arrogance that is clouding their judgement.
You want a tool to help the treasurer adopt "official" procedures? Get a copy of the PTOToday Treasurer's Toolkit binder (from this site). In the short term, print off the article from the PTOToday article archives called "Five Smart Financial Controls" - one of them is a written monthly treasurer's report.
www.ptotoday.com/magDay.html