Teenagers have nothing to do and spend time at stations, streets. Many take drugs or Alco.
Let city supports different activities, which can employ teens and be created for teen.
Example: quests (teens can learn smth new), sport events (to encourage them to be more active and try new sports), touristic events (know more about your country and other countries), events for entrepreneurship encouragement (meet with famous entrepreneurs and business representatives, play business games). All kind of events and activities, which can accumulate lots of young organizers (some get paid, others are volunteers) and lots of young participants.