1 “Learning to Read and Write: A Longitudinal Study of 54 Children From First Through Fourth Grades” by Connie Juel, The Journal of Educational Psychology, Volume 80, Number 4, Pages 437-447, 1988
2 Double Jeopardy: How Poverty & Third-Grade Reading Skills Influence High School Graduation. 2012, The Annie E. Casey Foundation study
3 UnitedStatesZipCodes.org