Data sgp is a set of longitudinal student assessment data that is used for the calculation of growth percentiles, student growth projections/trajectories and other analyses. The data is available in WIDE format that mimics time dependent data used by functions like studentGrowthPercentiles and studentGrowthProjections as well as in LONG format which facilitates the conversion to SGPstateData (Betebenner, VanIwaarden, Domingue, Shang, 2014). Using the long formats for operational analyses tends to be more practical given their size and ease of preparation.
Generally, student growth percentiles are based on comparisons of a current year’s test score to the performance of academic peers who also took a previous version of a standardized assessment. For example, a sixth grader might achieve a scale score of 370 on the state’s English language arts (ELA) test this year versus a 300 in the same test last year. While this is a significant achievement, it may not be indicative of student growth since different students have achieved similar raw scores on other assessments. Student growth percentiles place a relative value on these comparative gains, ranking the student’s performance in relation to those of his or her academic peers.
These measures are estimated by using a statistical procedure known as quantile regression to rank the performance of academic peers on a normative scale. This process is facilitated by the use of large samples of students tested on school-day tests from across the country and weighted to represent the demographic composition of students who take statewide assessments – including student race/ethnicity, gender, level of school poverty, and educational programs (e.g., sheltered English immersion and special education).
The results of the SGP estimates are compared to the student’s raw score on the current assessment to determine the growth percentile estimate for that particular assessment. The student’s percentile ranking on the current assessment is compared to the percentile rankings on the prior year’s assessment to calculate growth projections/trajectories and to compare the rate of growth of the student with the expected rate of growth for that cohort of students.
Additional information about the SGP estimates is provided in a series of SGPvignettes on this site. These vignettes explain how the SGP estimates are calculated, what they tell us about student learning and achievement, and why it is important to use them in comparisons of student achievement over time. The vignettes also provide links to other helpful resources that are available online. These resources include the SGP wiki and FAQ, additional vignettes and SGP webinars, and links to other SGP related web sites. Several of the SGP vignettes are available in PDF format and can be downloaded from this page. The SGP wiki includes an archive of past SGP webinars. This archive is a useful resource for those new to the SGP methodology and data. This archive is updated as presentations are made. The SGP wiki is also home to a series of articles and videos that are intended to help teachers understand the meaning and interpretation of student growth percentiles.