Oddly, to not pitch. From 60.5'. For my 13 year old son, who is in 7th Grade and just coming out of Little League and its 46' mound.
I started a thread on this topic last summer after my son's Little League All Stars, about whether pitching at 13 on the 60.5' mound was good or bad or indifferent. After consulting doctors, former pro pitchers, former college pitchers, a current MiLB AA Manager, other dads whose kids got injured their first year on the 60.5' mound, etc., my son and I decided he won't pitch from 60.5' this year. Just focus on 1st base and outfield (he's a lefty) and batting. We'll do some pitching drills on the side, and some bullpens starting at 50' feet and gradually moving back, but no pitching from the 60.5' mound. He will be there next year, when he's in 8th Grade.
He's a lefty, throws hard, has good movement (out on RHB), and I just don't see anything to gain from jumping straight to the 60.5' mound at 13, especially when he still has next year (8th Grade) before he hits High School. But I see plenty of downside. One friend's son seriously injured both his elbow and shoulder last season (2014), his first at 60/90, and he's still in therapy, trying to get ready to play this upcoming season. My son's best friend, also 13, pitched a little 60/90 this past Fall Ball, and he now has serious elbow problems for the first time in his life.