Just wondering...

Ok... this is a full story. so... it's the year 2018 and I'm in eighth grade. Since We'll be graduating soon, everyone is getting ready for the eighth grade dance. All of the girls are trying to find dresses and stuff and we are all super excited. This boy that is in most of my classes (we'll call him Jon) says that he likes me. I liked him at the beginning of the year but those feelings faded and now I think of him as a close friend. Anyways... My friend has been talking to Jon and has persuaded him to ask me to the dance. I really don't like him in that way though and I'm super nervous that he'll think that if I say yes I like him. I know how bad it hurts to be rejected and I really don't want him to feel that way. How would you recommend I let him down?