I attended a seminar at a local gifted conference led by a representative of the Kolbe Corp.  Kolbe designed a tool "to measure the instinctive action and problem-solving styles of individuals. This dimension of the mind, called "conation," determines the way in which each individual might feel most comfortable and perform best in undertaking any action." (
www.kolbe.com)
Among other things, Kolbe offers a diagostic questionaire (Kolbe index) online especially for kids.  This should determine their natural (and unchanging) learning style  (personality types -ala Myers-Briggs can change over time).  There is, of course, a fee for the online test but it is only about $50.  
My disclaimer:  I have not yet done the online test for myself or my kids.  In the class, we did a mini-assesment of ourselves which proved to be very interesting.  The class seemed to experience a lot of self-discovery and it prompted a lot of discussion.  I'm not sure if the online test would yield the same results without someone to moderate/translate it.  
If you are $50 curious, I think this is worth trying (IMO).  
