Caitlyn Jenner’s ultra-visible media “coming-out” transition, on a prime-time ABC special with Diane Sawyer and on the cover of Vanity Fair, was accomplished in her mid-60s, after a lifetime of conflict and reevaluation. Tonight’s Frontline looks at the issue from the other end of the age scale: Growing Up Trans talks to teens, and even pre-teens, as well as their parents, to explore, and explain, what it’s like when a child born as one gender identifies with the other. Check local listings.