I just needed to reply to R- you have totally described my daughter.  She is 11 years old and in 5th grade with locah.  I just had the same conference.  She is performing very well on the school scale but clear to all not to her full potential.  I am thinking it could be a little boredom.  We have asked the teacher to make voluntary extra credit more a required part of her daily work because she seems to rush through her regular work so she can sit and read a book in class.    Just one idea we are trying.