17? Is he missing his onions?
Our choirmaster can sing both tenor and countertenor. Believe me, they are handy to have in the house.
And he's perfectly masculine. My husband is a baritone who can sing in the countertenor range . . . and he's six foot six, 250 pounds, a 4th kyu in Aikido, and the proud daddy of two . . . any questions?
Might be the case that he's got undescended testicles. It's uncommon, but far from rare. I knew a guy with a really high voice in high school. Friend of a friend of mine. Turns out, years later, he had undescended testicles (a problem which I'm told later solved itself, but later than normal).