Can schools close the gap?

Missed the article from the WSJ that Econmist's View picked up back in January (maybe because of MAPP?).  The article is by a Nobel laureate economist arguing that increased investment in early childhood programs for disadvantaged children make economic sense.  The comments drift toward rants about vouchers, but I picked up on this part of the article:

Although much public policy discussion focuses on the failings of schools, a major finding from the research literature is that schools ... contribute little to the emergence of test-score gaps among children. By the second grade, gaps ... across socioeconomic groups are stable

This is a common failing in discussions of this type -- assuming from average data that schools can't remedy the gap.  Now, I am all in favor of developing proven, emphasis on proven, programs that can help get all children to school age ready to learn, but, right now, we do know that some schools and some teachers are managing to boost kids along the learning path at significantly higher than average rates and thereby reduce those gaps.  (See here.)  The point is, we need to be identifying ways to close the gaps between the most effective teachers and schools and those who are not nearly as effective.  This will help close the achievement gaps between students without holding any student back.