We have some parents that think the PTO is a Clique. So we put Volunteer on the back of our shirts. We went a step further and gave anyone who volunteered a shirt as well. Know at all school events, we were the shirts and anyone can ask a question.
PS.. we also have School themed t-shirts we wear for non-PTO sponsored events that we are asked to help with (i.e., field day, volunteering in classroom, state testing monitors) so we encourage volunteers to use the school t-shirt for non-PTO events so we don't look like snobs in our PTO shirts- but if it's our event we do PTO shirts.
We did black t-shirts with hot pink school logo on the front and on the back we did large print PTO in pink zebra print. We do it for the PTO board so we can get recognized at all of our PTO sponsored events and people know who to ask for help. It's been great. We ask our board members to wear them at events and i think it's a great morale booster. Just get cute and creative. We're thinking of changing our look for this year since some of us have worn our shirts out (that's a good thing- it means we're working hard). Good luck!