Thanks stchangg! I'm on Khan Academy's school implementations team and just wanted to add that Maureen, who is also on the school implementations team, is a former 6th grade teacher. This summer, we also have 2 experienced math teachers working with us to flesh out a significant amount of our math content: Chris Talone (teacher at Marlborough, a girls' school in LA, who taught 7 levels of math simultaneously with Khan Academy this past year) and Jesse Roe (teacher at Summit, a charter school in San Jose, who taught Algebra and Geometry to 9th graders with Khan Academy this past year). We're really grateful for their thoughtful contributions which are grounded in years of experience teaching math to lots of different types of students.