<i>subjects don't really start getting "split" subjectively (with different teachers) until middle and high school.</i><p>That's a mistake of the system in the United States. In many other countries, teachers specialize by subject in the elementary grades, the better to teach their subject effectively. See Knowing and Teaching Elementary Mathematics: Teachers' Understanding of Fundamental Mathematics in China and the United States<p><a href="http://www.amazon.com/Knowing-Teaching-Elementary-Mathematics-Understanding/dp/0805829091" rel="nofollow">http://www.amazon.com/Knowing-Teaching-Elementary-Mathematic...</a><p>for a detailed discussion of elementary math teaching, or The Teaching Gap: Best Ideas from the World's Teachers for Improving Education in the Classroom<p><a href="http://www.amazon.com/Teaching-Gap-Improving-Education-Classroom/dp/1439143137/" rel="nofollow">http://www.amazon.com/Teaching-Gap-Improving-Education-Class...</a><p>for a broader perspective on other ways to organize schools.