1) Slowness. Art education cultivates the habit of making time for one's private practice. It is so hard to take out 3 hours to do anything in peace & quiet … even reading a book is hard these days. But the habit of setting time aside to think and study is increasingly valuable and rare.
2) Personalization. What is learned in the classroom often stays in the classroom. It is becoming increasingly difficult to get students to internalize learning as part of their daily/personal life. However, I believe art education successfully bridges these two worlds or personal life and classroom life. Heros, values and ideas are introduced in the classroom that are carried over into personal life.
3) Informal Conversation. So much of learning is resume oriented and provokes the stifling question, "is this the type of thing that can be listed on a resume and used to get a job." However, there are so many valuable practices (like reading) that cannot be put on a resume, and are arguable the most important things. Within art school, students have informal CONVERSATIONS with teachers!! These conversations act as a model for how to think and process ideas. Having a model for this is one of the first steps towards becoming a sophisticated thinker.
4) Critique. Art education has a structured model for the older generation to rebuke/train/inform the younger generation in a way that goes beyond a "grade." Getting exposed to critiques cannot really be placed on a resume, but it is an excellent tool to negotiate interactions, resistance and values.
5) Multi-disciplinary study. Art pulls from so many other disciplines outside of itself. Its curriculum encourages reading history, learning psychology, analyzing literature, etc … While Business majors are often forced to take an Art History class, this is rarely seen as an experience that they can directly pull into their business practices. This cross fertilization is very difficult to quantify, but we all know the benefits.
Art education often gets ridiculed because it does not know how to demonstrate or measure it's efficacy. However, I predict/believe that "test" oriented education will dissipate, and all fields will move towards a training program that values broad & resilient thinking … more and more educational models will adopt many of these "art education" practices.