It's starting to break, as I recall -- he's hiding it as best he can. One of the boys in my son's choir did soprano solos remarkably late; he was by far the most reliable for a certain solo, having done it four years in a row or something, so he was retained in that role despite his voice having definitely started to change. I don't know whether that would have been as possible in speech (of course some adult men can sing countertenor).

I just asked my son and he said he thinks the boy was a sophomore in high school, so perhaps fifteen or sixteen.