I'd agree, except that these students probably didn't have optimal math instruction leading up to the acceleration either. The other factors have to include the environment, and in this case it seems that the poor area schools may be limiting many students. But even in general, the idea that simply accelerating average students will improve performance is ridiculous!
A
quick search for previous work of the authors turns up some interesting results, including these findings from a quick skim of two papers of theirs:
Classroom segregation increased in North Carolina from 2000/01 through 2005/06, continuing a general previous trend, and increased sharply in Charlotte-Mecklenburg ("School Segregation under Color-blind Jurisprudence: The Case of North Carolina", Clotfelter, Ladd & Vigdor, 2008). In addition, teacher quality is distributed very unevenly among North Carolina schools to the clear disadvantage of minority students and those from low-income families in areas including Charlotte-Mecklenburg ("Teacher Mobility, School Segregation, and Pay-Based
Policies to Level the Playing Field", Clotfelter, Ladd & Vigdor, 2010).
These authors seem to be chronicling long-standing problems in the Charlotte-Mecklenburg area and elsewhere in NC, which especially afflict lower-income students, which in the case of Charlotte-Mecklenburg probably form a large part of the students who underperformed as a result of the acceleration plan. In context, I'm guessing that the algebra acceleration was attempted as a quick patch for educational problems that probably begin in kindergarten for these underserved children.
