How do I tell someone they stink at singing?

There is a guy in our High School Choir Class, who absolutely is like the image of a guy who looks like he's never seen daylight. Every time he talks, he voice cracks. He hair is long and looks amazing greasy. He sings probably the loudest in the Choir, but it is very like cracky and very just bad. He tries out for every single solo, and when he's finished everyone looks around. It's very embarrassing to be on stage and knowing that people will hear him when it comes to a guy's only melody.

How can I tell this kid that he has no business being in the choir-class? Without hurting his feelings of course. I would upload a audio clip of him singing. But that's just plain mean.

This is a throwaway account just in case someone from my school happens to be a redditor. I even know my English teacher happens to be one.