Skateboarding problem...?

Ok..yea well i want to learn to skateboard. i've already really did start but I don't have a board. So i asked my mom if we could go to the store. She said for what? I said I want to buy a skateboard, but with my money. She was all like no...its to dangerous and stuff. I was like well in any other sport or hobby you can hurt yourself too. She said you have a greater chance in skateboarding and your not getting one! Well I want to skateboard alot! It will help me improve my bablace {{which i really need}} and it will get me outside excersiing, also it will give me something to do than sit on the phone or sit in front of the computer all day. How to I convince her I won't go out by our skatepark and go on the high ramps, just yet. I just wanna go to our little park and go up and down the sidewalk and parking lot and maybe do an ollie and a few kick flips? She is soo scared i'm gonna kill myself! she was like oh its for little kids! I was like umm no? I'm a teen! I won't hurt myself! Help