Know-How Exchange : Strategy

Why should parents that aren't currently members of the PTA join?
What don't they know about the organization that would dramatically affect their lives?

Rather than try to craft some clever wording, why not talk to those that aren't PTA members to learn why they aren't and how the PTA might do better to attract them.

I agree with Jay's last recommendation. A tagline that doesn't address the reason they haven't joined yet isn't much better than no-tagline. Where would your target audience see or hear the tagline? What would they need to know to decide to join? How does PTA membership benefit them or their children?

A tag line alone won't accomplish your goals: there needs to be more than simply a tag line. What specific objectives are you planning here?

Why did your current members join, this is where you need to start? If you are going to use multiple different programs to reach different type of prospective members, you may be able to tailor your message based on your target audience. If you hand out flyers at sporting events your audience already shows interest in their kids, so you may want to build on this.