An earlier post, Tallulah, mentioned the author Susan Assouline. A couple of publications by her are most appropriate on this topic. 'Developing Math Talent' and 'A Nation Deceived'. The first is available through most on-line book retailers. It is an excellent book, and through it you will also learn that she is the person probably most responsible for the concept of the modern day Talent Search for 4th, 5th and 6th grade students. She is also part of the group that first utilized the ACT Explore test (BTW, the 'death' of that exam has been delayed by at least one year) A very interesting description of the concept of above grade level testing that makes up the Talent Search concept. The second book is available either as a PDF download or as apparently a free copy at the following web site
http://www.accelerationinstitute.org/nation_deceived/get_report.aspx'A Nation Deceived' is a very profound book that addresses exactly the subject being discussed here. I highly recommend both publications...BTW, Dr Assouline was recently made Director of the Belin-Blank Center(University of Iowa), a leading advocate for academic acceleration. Three areas she lists as research interests are Mathematically Gifted Elementary Students, Twice Exceptionality and Academic Acceleration. I think she was also responsible for the development of the Iowa Acceleration Scale. Check out the Belin-Blank site online.
