No, not hopping up and down like in gym class!  Jumping Jacks is a finger independence exercise.  See your teacher for your uniquely customized jumping jacks exercise or purchase a String-O! booklet to see how Jumping Jacks can help improve your technique.

Options:
Sevcik Op. 1 Book 1 contains some great exercises that count in the "Jumping Jacks" finger independence exercise category.  Download it for free at imslp.org