The book examines data from the 2003 National Assessment of Educational Progress, or NAEP, as well as the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 and accounts for several factors such as race and socioeconomic status. The book observed that although "public school students started kindergarten with lower math achievement than demographically similar private school peers. By the time they reached the 5th grade, however, they were outperforming those same peers in the subject." EdWeek.org, May 13, 2014.
The study hypothesized two explanations for the public school advantage:
First, public school teachers are more likely to be certified, meaning they are required to continue to take professional-development courses that expose them to the latest research on teaching math.
Second, perhaps as a result of that professional development, their instructional approaches more closely align with recent studies suggesting that test results improve when students know how to reason and communicate mathematical concepts rather than merely learning to add, subtract, multiply, and divide. [Id.]The book has been poorly received by voucher advocates.