I'm 14, I get physically abused multiple times a day, every day at School. How do I stop it?

It's getting out of hand. I have asthma, and I'm in really bad shape, so I can't really defend myself, I also don't like violence. Sorry, I have nowhere else to turn to. The people who hit me, kick me, and so on, they smoke, some of them do drugs, get drunk, and smoke cigarettes. I tried reporting it, they just hit me harder, and so on, a lot of times, I get threatened to get killed. I reported one guy to the school Police officer, this happened today, after the police officer came to our class, and talked to him, after he came back, after the class, the kicked me, punched me, and more. In the end I had multiple bruises, my arms hurt a lot, and this happens on a daily basis. I'm tired of this. What can I do to stop it? This is a throwaway account. I live in Europe if that changes things.

EDIT: http://imgur.com/a/reflw#0 <--- Pics

EDIT2: Thank you, thank you, thank you, SO MUCH, everyone, for your responses! My mum, I have talked to her, we've decided to go to the school's staff, see the boy's parents, and we will talk with a police man present with the school's staff and psychologist, if that doesn't work, we will go to the police for a restraining order. If you have more suggestions, please feel free to tell me, I read everyone's responses.