State Rank, APD/DF3, and Percentiles

 

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Since the transition to Common Core in the state of California, CCSA has created and used the Average Point Difference (APD) to help schools and parents better understand SBAC scale scores and interpret growth. In 2017, the California State Board of Education adopted the same methodology used in APD to create the Distance from Level 3 (DF3) metric which is being used by the state as one of several accountability metrics. APD/DF3 are measures that compares a school's Smarter Balanced (SBAC) English Language Arts and Mathematics scale scores by grade to the state standard for "met". The score that is produced means that the average student in the school scored that many scale score points above or below the "met" standard.

We believe that rather than using a percent met or exceeded measure that incentivizes schools to only focus on "bubble students", the APD/DF3 instead encourages schools to help each student raise his or her score as high as possible each year. To further operationalize this information and increase its use and understanding by stakeholders, CCSA has translated the APD/DF3 scores at the school level into decile ranks which we refer to as State Rank. These decile ranks allow for an immediate understanding of how each school is performing relative to other schools in the state on standardized tests.

How is Average Point Difference or Distance from Level 3 calculated?
Because APD and DF3 are averaged by grade and subject, this enables fair comparisons across all grade spans and subgroups. Students receive a score on SBAC assessments which fall into one of four levels. Level 3 is called "Standard Met" which has been set as the goal for all students to achieve by the state. The scores reported publicly by the state give school and grade level averages. For the calculation of APD and DF3, a school's average SBAC scale scores are compared across grade and subject to the minimum standard scale score for the achievement level 3 or Standard Met (see more on the SBAC scale score ranges). The difference between a school's actual average score and the met score is then weighted by the percent of test-takers in each grade. These weighted differences are averaged across subject and grade to obtain a single APD/DF3 per school.

The DF3 produced by the state is for grades 3-8 and separated by subject. CCSA's calculation of DF3 includes a weighted average of grades 3-8 and 11 and combines both subject tests to produce an overall school level score. Average Point Difference is slightly different than DF3 as Average Point Difference is calculated based off of the CAASPP raw files released by the state in the fall of each school year and does not account for student continuous enrollment status. The Distance from Level 3 calculation accounts for student mobility and is calculated from the data files released with the update of the California Dashboard in the winter. In order to get charter schools data they can use toward their renewals petitions and because the APD and DF3 are highly correlated, CCSA produces APD when the data is available and updates all data points with DF3 at the point we are able to do so.

How are State Rank and Percentiles calculated?
After APD/DF3 is calculated, CCSA then places all schools in a lowest to highest rank order to produce a statewide percentile on a scale of 1 to 100. It is from this percentile that we determine the bottom 5% of all schools which are asked to participate in a Multiple Measure Review regardless of their performance on the other metrics within our performance framework.

We then take these percentiles and bin them into 1 to 10 ranks. For example, if a school is in the 6th percentile, it would be given a State Rank of 1. Whereas a school in the 92nd percentile would be given a State Rank of 10.

The APD calculation is based on publicly-reported achievement scores, as reported to the California Department of Education. CCSA does not produce APD/DF3 percentiles or State Rank for schools that are DASS, Alternative, or have fewer than 30 valid scores.

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