This is a relatively common occurrence, particularly involving teens. The standard for a change in custody is that there must have occurred some "material change in circumstances" in the life of the child that negatively effects the child, justifying a change in custody. Unless the father is able to show that there has been some change that justifies a change, no change will be made. Most of the judges understand the situation you describe and will generally hold that the child should remain in the home unless the non-custodial parent can show that to do so would harm the child. Chores and responsibility are hardly a threat of harm, yet lack of supervision and evidence of drug use is certainly a threat of harm. You should always consult with an experienced custody lawyer for advice, but based upon what you've described here, I wouldn't worry too much.
The standard to change custody depends on the physical custody arrangement. If you have joint physical custody the standard to change custody is bet interest. One factor under bet interest is the preference of the child if he is of a suitable age and capacity to state a preference. However, this is only one of many factors the Court must look at when considering best interest. I would document the drug use because it goes to capacity. If you have primary physical custody, Mr. Pickard is correct that the first prong Dad would have to establish is a material change in circumstance then if he overcome that hurdle the Court looks to best interest. I would suggest you consult with an attorney because from Judge to Judge there is a huge difference when it comes to teenage discretion issues.
The standard to change custody depends on whether you have primary physical or joint physical. Regardless, Nevada judges differ as to the weight they give a child's testimony, from not at all to based on maturity. I agree with you 100%. Teenagers should not be left alone if at all possible. And parents' parent; not children. But if he is smoking pot at 15, and having sex, you do have a supervision problem.