Last month's Wired magazine included an article discussing Benjamin Bloom and his metastudy of research on education.  Bloom compared students who had remained in classrooms with those who had been pulled out for individual instruction.  According to Wired Magazine, "Education scholar Benjamin Bloom figured out [that] students given one-on-one attention reliably perform two standard deviations better than their peers who stay in a regular classroom.  How much of an improvement is that?  Enough that a student in the middle of the pack will vault into the 98th percentile."  (Wired, p. 129, Aug. 2011)