How do I convince my parents to let me have a airsoft gun?

I have a little problem with this, My parents won't let me have a airsoft gun, The reason why is that recently I got a cello BUT I earned it for my grades and showing I am responsible to handle one. But see I have shown a lot of interest in the sport from my friend. the problem is that they say "I will shoot someone or a window" Even when they were at my friends they saw a little cheapo pistol and still thought I would shoot something out. How should I convince them? and I am also 13.