George Will’s got the answer in his column. Last paragraph at the bottom:
“He [Paul E. Barton] has estimated that about 90 percent of the difference in schools’ proficiencies can be explained by five factors: the number of days students are absent from school, the number of hours students spend watching television, the number of pages read for homework, the quantity and quality of reading material in the students’ homes — and, much the most important, the presence of two parents in the home. Public policies can have little purchase on these five, and least of all on the fifth.”
Something that should be obvious to someone with the most basic observation skills but, in any case, sadly, GCS can implement all the policies it wants to try and close the achievement gap but the real way to do that begins at home. Or they could just push all of the high achievers out of the public school system and then the gap would close itself!