This is a very hard question to answer since if we knew the right answer, we would not have any drug problems. Therefore, no answer that we give here can possibly serve to eradicate all drug problems in a community.
In order to think about how to address drug issues, we first have to think about why kids get involved in using drugs. Some kids get involved in drugs because they do not feel good about themselves or about their futures. Some get involved because they lack role models who can show them how to live drug free. Others get involved because of peer pressure. Still others might get involved simply because they are bored.
Good programs to address drug issues would need to address these factors. We might provide kids with things to do after school. Extracurricular activities and things like Boys and Girls Clubs would do this well. We might provide kids with role models through programs like Big Brothers and Big Sisters. We might provide programs in which kids learn how to deflect peer pressure. We might try to provide more tutoring for at-risk kids so that they could feel better about their abilities and their potential futures.
Of course, these things are not cheap or easy. They are also not guaranteed to work. However, they are things that could make a difference.