Since state school ratings were released last month, the NOLA Public Schools district has been touting its newly released “graduation rate index” of 86.4, a marked increase from the year prior. But that number — considered a B on the state’s A-F rating scale — is not New Orleans’ graduation rate.
The graduation rate is the percentage of students in a cohort that graduate on time. The index, on the other hand, is a state rating tool. In contrast to the 100-percentage-point graduation rate scale, the graduation rate index — like other state grading measures — has a 150-point scale. To determine the index, the state applies a multiplier to the graduation rate.
The district’s most recent graduation rate is actually 77.8 percent, a nearly five-point improvement from the year prior. But its graduation rate index jumped nearly 21 points.
That’s because, for the first time in recent history, the district surpassed a 76 percent graduation rate, a state-created threshold, which in turn amplifies the index score the district is showcasing.
The increase in graduation rate index was lauded recently at an Orleans Parish School Board committee meetings. In much smaller font on the same slide, is the district’s most recent graduation rate, a more universally understood metric.
The state’s threshold graduation rate of 76 percent is where the gain of one point in the graduation rate translates to a 1.1-point gain in index score. Rates below 76 percent only receive 0.9 points for each graduation percentage point.
|Graduation Rate||Graduation Rate Index Formula|
|0 percent to 75 percent||Graduation rate x 0.9|
|76 percent to 90 percent||Graduation rate x 1.111112|
|91 percent to 100 percent||Same formula as 76-90, plus 5 points for every percentage point above 90.|
That means with any graduation rate above 76, the index will be higher than the actual graduation rate. And with any graduation rate lower than 76, the index will be lower than the graduation rate. New Orleans jumped from one bucket to the next this year, hence a 20-plus point gain.
For high schools, the “graduation rate index” is a metric that goes into state performance scores. Those annual ratings carry high stakes for charter schools, which are allowed to stay open based chiefly on academic performance. The state set up the index to align with certain A through F letter grades on the state’s 150-point scale, Louisiana Department of Education spokeswoman Sydni Dunn explained.
“For example, a 90% graduation rate results in a 100 graduation rate index, equivalent to an “A” in 2025,” Dunn wrote in an email “A graduation rate below 75% results in an index below 70, or a ‘D’ or lower letter grade.”
“The multipliers exist to translate a graduation rate between 0-100% to an index between 0-150 that aligns to the letter grade scale,” Dunn wrote. “The 76 is just a result of scaling so that a 67 or below was an F.”
A 67 percent graduation rate is a federal threshold at which a school or school district should be targeted for intervention by the state, she explained.
The NOLA Public Schools district’s graduation rate did increase from 2017 to 2018 from 72.9 to 77.8. (Graduation rates used in school ratings lag one year behind.) But because the district crossed that 76 percent threshold, the index score shot up from 65.6 to 86.4, almost 21 points.
“From the class of 2017 to 2018 we saw a 4.9 percentage point increase, putting us from below that cut off to above that cut off,” NOLA Public Schools Communications Director Tania Dall wrote in a statement attributed to the district. “If the multiplier was the same regardless of the rate, then the score change would only have been about 5 points.”