How do I get this boy to leave me alone!?

There's this boy who likes me..... and well i don't like him at all. We have a cl together (science) I don't like him even as a friend because he picks on a lot of people for NO reason....... and well i'm only 11 and he ask me out about a week ago and i said no. Then after that like 4 days after he kept giving me weird looks like curious looks and it kinda freaks me out! Later, then in science cl when i got up to sharpen my pencil he was looking at my and i felt uncomfortable. My friend said he was glancing at me every 5 seconds........... How do i get him to just give me some space??!!