How to convince them to get me an iPhone 5s?

Well I'm 14 years old, nearly 15 and i would really like an iPhone 5s for christmas. Christmas is in 11 days and i didn't get the greatest report from school. I have been asking for a phone for nearly 2 years now and still haven't got one. Is there any way i can convince my parents to get me one?

Not with poor grades.

Perhaps YOU should save up and buy a phone yourself?

Get an android.

I always got my parents to get me a big ticket items by finding them on sale, used, or buying them off of a friend. (2nd hand Nintendo 64 is still a Nintendo 64, yeah?) iPhone 4 or 3GS is still an iPhone with iOS7, yeah?

Get the neXus 5.

IPhone 5s is better