Today's New York Times has a fascinating article on the mostly European concept of practice firms. As the name implies, practice firms give people practice in doing work.
This seems to align well with the research on learning that suggests that learning in a realistic context, getting lots of retrieval practice and feedback, and many repetitions spaced over time can be the most effective way to learn. Of course, the context and practice and feedback have to be well-designed and aligned with the future work of the learner.
Interestingly, there is an organization that is solely devoted to the concept. EUROPEN-PEN International is the worldwide practice enterprise network. The network consists of over 7,500 Practice Enterprises in more than 40 countries. It has a FaceBook page and a website.
I did a quick search to see if there was an scientific research on the use of practice firms, but I didn't uncover anything definitive...If you know of scientific research, or other rigorous evidence, let me know...