This suggestion (presented at 2006 YIH COTS) is for schools that might be reluctant to work with you.
The idea is to propose helping train a school quartet to sing the national anthem so that they can sing ahead of school events. Pitch it as a tremendous way to promote that teacher's vocal program—and that the singers become instant celebrities.
The local chapter should be willing to purchase the music and practice tapes, as well as coach the singers several times. Because it would be performed a capella, there would be no issue of having accompaniment. The singers will love it, the students will love, the parents will love it, the music educator will love it. So will you.
Doesn't that sound like a "win win win win win" result?