EL CERRITO, Calif. (AP) — In some ways, Rainbow Day Camp is very ordinary. Kids arrive with a packed lunch, make friendship bracelets, play basketball, sing songs and get silly. But it is also unique, from the moment campers arrive each morning.

At check-in each day, campers make a nametag with their pronoun of choice. Some opt for "she" or "he." Or a combination of "she/he." Or "they," or no pronoun at all. Some change their name or pronouns daily, to see what feels right.

The camp in the San Francisco Bay Area city of El Cerrito caters to transgender and "gender fluid" children ages 4 to 12,...