Our elementary PTO letterhead had a clipart picture of school house and the phrase "Help Us Help the School" so that sort of became a slogan/brand on our literature.
We have a logo with a drawing of our school building (cute) and big red PTO under it. Our slogan is 'building on a tradition of excellence". We use this logo on all of our publications and forms for continuity, and also offer laminated name badges for room parents and PTO officers/committee chairs with our logo.
Another popular slogan that we use is "Get Involved, Get Infromed, Get Excited!"
Our groups name is Parents At Lanigan School (PALS) inc. we are a 501c3 non profit in our fifth year. We don't have one slogan that we use we try to come up with a new 'marketing' program each year, that we use for that year. Example one year we used "have a slice of PIE (parent involvement in education) or this year was "do you have a hour or two?" hope this answers your question.
"When you stop learning you stop growing."