The video that changed Alaya High’s life is, by production standards, rather elementary.

Shot on a phone, handheld at a slightly off-kilter angle, it shows the tiny 11-year-old girl as she sits in the passenger seat of her father’s car. It looks, in fact, like the sort of video every parent has taken in the spur of the moment. Footage fired off to a spouse or a grandparent, meant for a space no more public than a group chat, destined for an emoji reaction or, if the recipient is feeling generous or a little bored, a follow-up question. The content, though, is pretty extraordinary.

THR Issue 18 Kids Power!

Lay Lay, as she calls herself, is rapping with the talent and tenacity of someone twice her age. A speck of a thing, she’s checking herself out in the car’s visor mirror (“Hold on, Daddy, lemme make sure...