[29] The 2004 and 2006 editions of Science and Engineering Indicators included an indicator of college remediation. However, this indicator cannot be updated for this edition because there were no new data available at the time of preparation for this chapter.

[30] NCLB requires that states include graduation rates in determining adequate yearly progress and calls for measurement of on-time graduation that explicitly excludes GEDs and other types of nonregular diplomas from the counts of graduates.

[31] Researchers examined several proxy measures of on-time graduation rates (Seastrom et al. 2006a). Although none of them is as accurate as the on-time graduation rate computed from a cohort of students using student record data, one of the methods, called Averaged Freshman Graduation Rates (AFGR), most closely approximates the true cohort rate and is used here. AFGR measures the percentage of an incoming freshman class that graduates with a regular diploma 4 years later. The incoming freshman class size is estimated by averaging the enrollment of 8th graders 5 years earlier, enrollment of 9th graders 4 years earlier, and enrollment of 10th graders 3 years earlier. This averaging is intended to adjust for higher grade retention rates in the 9th grade.