Let your Festival Quality Storytellers know you are proud of them and give them opportunities to continue to polish their stories before they appear at the Festival. A few suggestions (we're sure you can think of more):
Feature them telling their stories on your school's morning show.
List their names on the marquee outside the school.
List their names in the school or PTA newsletter (and make sure you include information on the Festival so everyone can be there to cheer them on!).
Let students tell their stories to other classes.
Take a group to tell at a preschool or nursing home.
Feature them in a school mini-festival.