The NGA's adjusted cohort formula was agreed to by the governors of all 50 states in 2005. Iowa is currently one of 20 states that have already implemented the NGA formula, with the goal that all 50 states are using a cohort rate by 2012. Iowa, along with 30 other states, previously used a formula called the "leaver rate calculation."
"There has long been a debate about how graduation rates are calculated and what states should use," said Iowa Department of Education Director Judy Jeffrey. "While Iowa has consistently had one of the top graduation rates in the country regardless of which formula was used, the NGA formula provides a common platform for state-to-state comparisons as well as a more accurate account of the achievement of our high school students."
The NGA formula requires a state to assign each student a unique state identification number, a sign of a state's success in its ability to collect educational information. In Iowa, school districts have used student identification numbers since 2004, which allows school districts to keep careful accounting of each ninth grader as they progress through high school. This also helps determine when a student graduates, even if they moved to a different school district in the state during their high school career. Iowa's class of 2009 is the first group of students to have had an assigned statewide ID number for five years.
"Today, Iowa students who graduate early or graduate after moving between several school districts can be assured their accomplishment is reflected in state-wide graduation rates," added Jeffrey.
According to the NGA formula, the class of 2009 had a graduation rate of 87.2 percent. This means that 87.2 percent of the students who started ninth grade in 2005-2006 completed high school in Iowa in four years or less.
While 87.2 percent is the 2009 four-year graduation rate, it does not mean that 12.8 percent of the students have dropped out. There are students who remain in high school more than four years.
The NGA cohort rate sets a new baseline in Iowa for comparing graduation rates year to year. Therefore, comparing the 2008 graduation rate to the 2009 rate is inaccurate and not an "apples to apples" comparison. Next year, additional information will be available about changes between annual graduation rates.
For more information on:
- Iowa's NGA cohort rate calculation, please see "Iowa High School Graduate Rates Information."
- Frequently Asked Questions about Iowa's graduation rate, please click here.
- 2009 graduation rates by districts, please click here.