Starting next year, girls can decide whether to become a Girl Scout or a Boy Scout. But a handful of girls — kind of secretly — have already made that decision. How one 10-year-old girl got a head start on joining a boys-only club. And why her twin sister decided to stay with the girls. Guests: Elsa Moock, who joined the Boy Scouts last year; her twin sister Clio; their father Alastair; and Dylan Bates and Harry Krygowski, two boys in Elsa’s troop. For more information on today’s episode, visit nytimes.com/thedaily.