what Taffeta said. Join the PTA and get a feel for it. All these people who automatically assume the worst!
I've been on the PTA since I joined the school. Got corned in the playground on the first day and am really glad. I've got to know the school, the staff and other parents. It is so hard though.
It is a lot of hard work to put on fundraising and community building events, but you do it for the kids and for the school. An involved parent community makes for a much nicer school environment overall.
But after you've worked your butt off, spending most of your time just trying to get people to help on stalls, it is REALLY pissy to have people criticise because there weren't enough events/stalls on, or some of the games were only open for some of the time, or to be told that what we should do is X.
Supporting the PTA by making a cake and coming along and spending money IS appreciated, and it IS fabulous. But even if it is only once a year, PLEASE volunteer to man the cake stall/summer fair stall or just help out.
We are contantly having to cancel things, or scale back. For example our school is on two different sites, and we're constantly being criticised because we only hold, say, a cake sale at one site. But the truth is, we just don't have enough volunteers to run two cake sales at two sites.