Is my arm mature enough to throw a slider?

Question
Hey,

I am 13yrs old, I throw about 65-70 and I was planning on joining my Junior high baseball team. Most pitchers on my last club team everyone was throwing all different kinds of junk, and I tried a slider about 2 months ago. It brakes about 4inches in and about 3 down, but I am not very sure if I should be throwing this pitch yet.
Thx for listening
        Grady Bain

Answer
I would have to say "No". At only 13, your arm is not ready to throw a "real" slider. Keep it in your back pocket but work right now on commanding your fastball to both sides of the plate and learn a change-up.
I'd wait a few more years until you start throwing that slider on a regular basis. Mix it in every now and then, but try not to rely on it too heavily. Your arm will thank you
-Jon