There is a notion indicating that work experience is more effective way to accomplish a skill than attending a school. I partly disagree that for some reasons.
The best method for learning a skill, based upon its nature would be varied. For example, when we are talking about learning programming, at early stages there is no difference between taking a practical course or an internship, and even sometimes academic expertise may be required to take part in an intern position. Also, when it comes to the other professions a certificate of training course will be mandatory. Although academic background is necessary for job vacancies, it is not deniable that by starting a career the advancing phase will start.
Furthermore, workplace atmosphere is more competitive and often a superior assumes that his employees already are proficient in their jobs and expects them to complete assigned tasks by specified deadline. So, there is not enough time for subordinates to build up new skills. While participating a class provides an interactive environment to learn an expertise which secure your progress.
In conclusion, there is no precedence between learning an expertise through academia or industry, and in my belief work experience is complementary to education.