I have a lot of creepy guys hitting on me what do I do?

So I'm just a bit scared that one day some guy is gonna pounce on me! I'm always told that I'm really good looking and attractive. I go to an all boys school so I'm always getting hit on by guys. I just don't know how to tell them I'm not interesting in them because some of the guys are abit obsessive about me, which means they could do something scary. How do you deal with all this unwanted attention!? I'm not over exaggerating so please!