Want a penpal, but not sure about security? is it safe ?

I've always wanted a penpal, and now I'm ready to try and get one but my mom is concerned about security. As much as I tell her that no matter where I go, people with ill intentions will be there she won't listen. How do I find a penpal, while decreasing my chances of bumping into a creepy person? Also how can I convince my mom to take the risk and change her mind? 

P.S. I'm 17 if that helps, and it would be nice if people could include any website references
I'm looking for via email or snail mail ( pen and paper) penals
 i'm looking for a penpal via email. 
and no, i am not creepy person. 
just tell your mum that you won't give out ''personal'' details, eg: address. yeah?
Um....I don't know what to tell ya. The worlds full of creeps
do you mean an actual pen and paper/writing letters penpal? 
most schools and colleges will have a list of students around the world looking for penpals 
their school or college put them on the list when asked, so they know its a bona fide student 
so yours would/should do the same