Your 11-13 year-old child asks you if it's alright if they masturbate. What would your answer be?
Why?
My kids never asked me if it was okay. It would become apparent in one way or another. Husband and I never made a big deal out of it since the kids have always been discreet about it.
And, in my opinion, masturbation isn't something to worry about. They've known what it is for quite some time since I'm very frank about sex and sexuality and letting them know their bodies are not dirty, horrible, shameful, etc., but that they must be clear with themselves and others what their boundaries are in regards to anything intimate.
The only parental guidance I've stated regarding masturbation is 1) don't do it in public, and 2) don't let it become a priority over school (at the ages 11-13). But in the privacy of their own bedrooms, in their free time, masturbation is harmless at worst and beneficial at best.
At that age, too, it's certainly good to understand and explore at their own time, and knowing what are their own bodies' likes, dislikes, and "absolutely not" areas. Hence, I fully support a young pre-teens or teens decision to privately play and leave them alone / give them space and freedom. I think it's an effective and healthy way of discovering ones own personal sexual boundaries.....and in so doing, will be in a head start in communicating desires and boundaries to future partners.