What is a healthy weight for someone who is 13 sex and height?

We don't know you, and cant answer that for you. It depends on how much fat/muscle you have and other things. Sorry if it comes off as a dick response, but what im trying to get across is this question is better suited for your physician. They have a graph of how much weight and height you've gained since you started seeing them and they can give you an extremely acurate answer.