Of all the curriculum approaches I've encountered as an educator, the International Baccalaureate Primary Years Programme provides the most comprehensive, academically focused, and highest levels of thinking for elementary age students.  In addition, student engagement levels are extremely high, and--in order for the program to succeed-- teacher planning must be collaborative.  In action, this approach is a beautiful sight!  I recommend a review of this approach for the many children and teachers who are eager to tackle critical thinking, advancement at a quick, but manageable, pace, and global awareness.