art nudes

My boyfriend really wants to take part in an art project which involves him modelling nude, he asked me if I'd be okay with it and straight away I said no but he's still considering it. The art project will be displayed at the sixth form college I used to attend and where he is still a student, I'm just not comfortable with his body being seen by hundreds of people, some of which I know. I understand that it's all about empowerment but i just can't stand by it. 
How can I explain why I'm uncomfortable with it?