New Hampshire does not appear to have any provision for a minor to emancipate; it does recognize emancipation orders as granted by other states.

Your parents are worried because you aren't doing well in school, and are even failing some classes. They are encouraging you apparently to take academic classes and you don't like those classes (or is it extracurricular activities). They are concerned that your poor performance in school may indicate that you're using drugs. You're probably spending a lot of time in your room with the door closed - playing on the Internet or playing video games - and somebody has probably suggested that this is a "sign" of withdrawal from the family and drug use. Welcome to the world of parents and teenagers.

If you really want to be emancipated, you're going to have to get your act together - even in states which permit emancipation you have to show yourself capable of handling your own social and financial affairs. Flunking classes and getting bad grades will generally convince the court that you're not a good candidate for emancipation.