Well, if this guy is obviously interested in singing, I wouldn't actively discourage him by basically telling him he stinks (which is what "you're not at the level of the rest of the group" basically means, even though it may be true). I'd avoid pieces that present solo opportunities for his range, as one poster suggested, and maybe recommend a private voice teacher, not in a mean way, but in an "I had a lot of success taking lessons with so-and-so," type of way. I don't sing seriously myself, outside of the university choir, but I've played the clarinet for eight years (closer to nine by the time I graduate), and I've been both in the position of being the "underdog" (since I was always way too ambitious), and more recently, in the position of being the.....umm......not-the-underdog, and sometimes as the not-the-underdog, when people ask, you have to tell the truth, not in a brutal way, but in a TRUE way. If someone came up to me and told me they wanted to take lessons at Bishop's, with my teacher, and that person had no rhythm, crummy air support, and played on a plastic Yamaha clarinet with Rico reeds, well, I'd probably have to tell them straight up that they'd almost certainly have trouble here.