is it good for 13 year olds?

if they have oily skin, blackheads, breakouts etc then yes I think this would be helpful and safe for a 13yr old. There's no harsh or strong exfoliating ingredients in this, it uses sulfur with clay and fizzes up to clean out pores. But to be safe, do a small patch test first to make sure there's no bad reaction before using all over the face. You should patch test everytime you try a new product.