How to Interpret Student Growth Percentiles

Student Growth Percentiles (SGP) provide a picture of a students growth over time by comparing a student’s current test score to the average of academic peers with similar prior test scores. In this way, SGPs help you identify if your student’s performance is on track to reach or maintain proficiency on state assessments. In addition, the SGP trajectories are updated regularly to reflect the most recent information available for each student.

SGPs are a powerful tool in helping to inform instructional decisions. While they are complex to compute, they provide a summary of students progress in terms that are familiar to teachers and parents. This article discusses how the SGPs are computed, the value of these percentages in making instructional decisions, and some common caveats to consider when interpreting the data.

The Wyoming Department of Education Fusion Portal provides reports and Excel files containing the SGPs for all students in the district. The SGPs are based on the most recent available student assessment data. The Wyoming Department of Education has adopted SGPs in grade levels 3-8 and 11-12 for all students, and the SGPs are updated frequently to reflect the most recent information about each students progression towards proficiency.

The SGPdata package, installed automatically when you install the SGP package, includes four exemplar WIDE formatted data sets (sgpData, sgptData, sgpData_LONG and sgpData_INSTRUCTOR_NUMBER) that are utilized by the lower level functions studentGrowthPercentiles and studentGrowthProjections. These exemplar data sets serve as a model for how to set up longitudinal (time dependent) data for your own analyses.

Each exemplar data set consists of five years of annually, vertically scaled, student assessment data for three content areas. The first column, ID, provides the student unique identifier and the remaining columns provide standardized test score values for each of the assessment occurrences. These values are then aggregated to generate the student growth reports for each individual student. The vignette for the SGP package provides more detailed documentation on using long format data for your own SGP analyses.

SGP calculations require that you have access to a complete and accurate data set of student assessment results for each year of instruction. For this reason, SGP analyses can only be conducted with data sets that are released to the public for all districts. The sgpData vignette describes how to construct such a data set from the public data set provided by the Wyoming Department of Education Fusion Portal. In addition, the SGP vignette demonstrates how to use the higher level functions prepareSGP and abcSGP, which simplify and consolidate the 6 steps of the source code into two function calls for operational SGP analyses. These functions also work with WIDE formatted data as well, but for operational analyses we recommend the use of the LONG formats sgpData_LONG and/or sgptData_LONG.