Most Shabbat worshippers expect decorum. But Adat Ari El's new Jump-n-Jive minyan is different. Its founder, Aaron Kaychuck, describes the monthly Saturday morning service as "upbeat neo-Chassidic egalitarian." The service is unusual partly because it combines traditional Conservative liturgy with exuberant song and dance, set to the beat of an African hand-drum. It is also distinctive because Kaychuck, who leads the congregants in prayer, is 15 years old.