Sammis White, Ph.D (full report here: 250K PDF):

study of 23,000 third-, fourth-, and fifth-grade students in the Milwaukee Public Schools showed that “among low-income students tracked between third and fourth grades 2002-03 to 2003-04, those with five years of Direct Instruction (DI) increased their math scores by 6.6% whereas non-low-income students increased their scores by 4.7%. This difference is statistically significant and is evidence of substantial progress.” These results are reported in Education That Works In The Milwaukee Public Schools: The Benefits from Phonics and Direct Instruction, by Sammis White, Ph.D. The report was released today by the Wisconsin Policy Research Institute.