My wife's done her Master's thesis (http://goo.gl/rceG8) on Gardner, Beane, and Hayes-Jacobs, looking at integrated curriculum (specifically in/through the art classroom) and one of the major themes from her research has shown that teachers aren't always comfortable with multiple techniques for the same subject. If some students respond better to math concepts when they're presented through artistic methods (i.e. geometry perspective drawing), some math teachers are resistant because they fear losing their jobs to art teachers, and art teachers fear losing art classes if they get swallowed up into the other curricula.
And even more importantly, a teacher who can master the multiple techniques and/or disciplines needed to teach the "whole child" and the full spectrum of learning styles, are not produced in high quantities by the education departments at most universities, and are typically capable of seeing their value in fields that require multi-discipline expertise and offer better value for their services and moving to those fields. Or, if not a true master in many fields, but above average in more than one, become prime targets for advancement OUT OF THE CLASSROOM and into administration.
I don't know what the solution is, though my wife has some ideas that might help. Overall though, there's a huge barrier to implementing reforms that address these types of issues.
