“Jaysea is going to change the world with her kindness and brilliance,” said Kim Bauman, 39, founder of the One Love Movement, a yoga nonprofit that Ms. DeVoe has volunteered with. “We look up to her for being a leader in the community at age 13.”

Raised in an unconventional household where her father manages surfers and musicians, Ms. DeVoe fell in love with yoga when she was 8 after taking children’s classes at the local Y.M.C.A. Her yoga mentor, Lindsay Russo, encouraged her to become an instructor. “What I saw in her that made her seem so ready for the training was a desire and an enthusiasm,” Ms. Russo said, adding that Ms. DeVoe exhibited “a very focused, calm energy” and “an old soul.”

Her vinyasa flow classes invoke nature as a theme. “I’ve lived by the ocean my whole life so I’ve really liked just going with the flow and incorporating that into how I teach,” said Ms. DeVoe, who calls her class Sea Vibes Yoga. She burns sea-scented incense and plays feel-good tunes like Bob Marley’s “One Love/People Get Ready.”

The nautical references extend to specific poses. She teaches students to modify a downward dog by spreading their fingers (“like starfish crawling along in the ocean”), and to relax by imagining themselves as pieces of kelp (“feet grounded, the body going along with the current”).

Students appreciate her accessible approach. “Even when I am outside of her class, or when I have a bad day, I can always hear Jaysea’s voice,” said Kendall Israel, 14, a ninth grader from Houston who spends her summers in Southern California. “She tells you to let go and be in this moment.”