My 13 year old wants to decide who to live with.

No child ever gets to decide who they want to live with, regardless of their age. However, the older they get, the more weight their wishes are given. This is especially true if there is a legitimate reason for that and they can articulate it in a mature and intelligent way. You would need to file a motion to modify custody and/or placement. Your best option is to consult with an experienced family law attorney who can review all of the facts and advise you as to your best course of action.

Contrary to popular belief, a child can never choose where to live. Oftentimes, the child(ren) may wish to live at the house with less discipline, for instance. However, child's wishes are a statutory factor in legal custody and physical placement, and generally the guardian ad litem and subsequently court will give credence to the child's wishes, especially if those wishes are articulated well by an older child. However, the court's decision will ultimately be directed by what is in the best interests of the child.