In their new NBER study, “The Unwavering SES Achievement Gap: Trends in U.S. Student Performance,” Eric Hanushek, Paul Peterson, M. Danish Shakeel, Laura Talpey and Ludger Woessmann conclude,

Two startling results emerge from this analysis of long-term trends in student achievement gaps and levels across the SES distribution. First, gaps in achievement between low and high SES [socio-economic status] groups are mostly unchanged over the past half century. Second, while gains in the level of achievement are steady and significant at the 8th grade level, they have not translated into gains at the end of high school. Thus, the continuing unequal opportunities of the haves and the have nots are not compensated for by enhanced overall opportunities.

The authors caution that their study is not designed to determine the cause of this stubborn achievement gap.  But they point out that the current system is clearly not working for disadvantaged children.