Work ethic is developed before that first job. It's the way someone is raised by their parents.Having a memory lapse, but read a book that stated the most influential job a person could ever get is their first job. For may, the first job sets the standards for that new worker--- for life.
Have a first job that has high standards and discipline, that young worker may have high standards and discipline in everything they do, for the rest of their life.
A teen ager who has spent their time on the sofa playing games, all I got to say is good luck with that individual.