How can i convince my parents to let me get a Dirt bike?

Well im 15 and I have asked my parents for YEARS if i could get a drit bike... with all answers being a flatout "NO!" They wont let me get one because they are afraid i will get hurt, (i know, they are good parents) but i really want to expand my knowledge in recreational motor vehicles (Quads,... show more Well im 15 and I have asked my parents for YEARS if i could get a drit bike... with all answers being a flatout "NO!" They wont let me get one because they are afraid i will get hurt, (i know, they are good parents) but i really want to expand my knowledge in recreational motor vehicles (Quads, Motorcycles etc.) just because i want to learn some of this stuff... I am always hearing stories from my dad about HIM having a dirt bike when he was younger and it is starting to make me a little upset because it is kind of a tease at what i would like to do... but that goes back to the reason they wont let me get one, they say "its too dangerous" and i do realize there are some risks that accompany riding any kind of motorcycle... TL:DR I just need some reasons why my parents should let me get a dirt bike and make them feel like i can be safe riding one...
Update: And please, dont say "Get good grades" because i am an A/B student...
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