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Student Growth Percentiles

This page provides an overview of student growth percentiles, a new method of measuring student academic growth introduced by OSPI in March 2013. This page will answer the following questions:

What are student growth percentiles?
A student growth percentile (SGP) describes a student’s growth compared to other students with similar prior test scores (their academic peers). Although the calculations for SGPs are complex, percentiles are a familiar method of measuring students in comparison to their peers.

Washington’s state assessments were not vertically scaled before the 2014-15 school year. This means the different MSP grade level tests did not combine to form one long yardstick for measuring growth in math or reading from one grade level to the next. Therefore we could not measure a student’s absolute growth by comparing last year’s scale score to this year’s. Instead, we began to measure student growth by calculating student growth percentiles that indicate the amount of growth a student made in a testing subject over the course of one year, relative to their academic peers. The student growth percentile allows us to fairly compare students who enter school at different levels. It also demonstrates a student’s growth and academic progress, even if she is not yet meeting standard.

A student growth percentile is a number between 1 and 99. If a student has an SGP of 85, we can say that she showed more growth than 85 percent of her academic peers. A student with a low score on a state assessment can show high growth and a student with a high score can demonstrate low growth. Similarly, two students with very different scale scores can have the same SGP.

How are student growth percentiles calculated?
Student growth percentiles are measured by using a statistical method called quantile regression that describes the relationship between students’ previous scores and their current year’s scores. For more discussion of the SGP model, please see the technical resources on the Student Growth School and District Resources webpage.

To whom are students being compared? What is an “Academic Peer”?
For SGPs, a student is compared to his/her academic peers. A student’s “academic peers” are all students in Washington state in the same grade and assessment subject that had statistically similar scores in previous years. In other words, they are students that have followed a similar assessment score path. Students are only compared to others based on their score history, not on any other characteristics, such as demographics or program participation. A student’s growth percentile represents how much a student grew in comparison to these academic peers.

What is a median growth percentile?
The median growth percentile summarizes student growth percentiles by district, school, grade level, or other group of interest. The median is calculated by ordering individual student growth percentiles from lowest to highest, and identifying the middle score, which is the median. The median may not be as familiar to people as the average, but it is similar in interpretation – it summarizes the group in a single number that is fairly calculated to reflect the group as a whole. (Medians are more appropriate to use than averages when summarizing a collection of percentile scores.)

Are SGPs available for students that took the MSP/HSPE/EOC in 2013-14?
In the fall of 2014, OSPI provided student growth percentiles for the approximately seventy percent of third through eighth grade students who took the MSP assessment in the spring of 2014. SGPs were calculated using previous year(s) of data as a baseline. For more details on this methodology, please see below. For 10th grade students who took the HSPE and students that took the Algebra and Geometry end of course assessments, SGPs were provided, even if they also took the field test. Student growth percentiles were not calculated for the students who only took the field test, as there were no individual scores assigned. This group comprised roughly thirty percent of Washington’s third through eighth graders in the 2013-2014 school year.

How are SGPs calculated when there is not a state-wide set of scores, as in 2013-14 due to the SBAC field test?
OSPI was able to calculate SGPs for students taking the MSP despite not having a state-wide representation of scores in the 2013-2014 school year. In previous SGP calculations, (2010-11 through 2012-13), students were only compared to other students in their cohort (other students in that same year and grade). However, OSPI used an alternative method in 2013-14, referred to as baseline-referenced SGPs. Baseline student growth percentiles combine multiple years of student data into one super-cohort. This is a slight nuance in how SGPs are calculated, but the overall interpretation of SGPs is the same and they can still be used to communicate another view on how students are progressing.

Can we still compare scores across years if the tests change?
Yes, because we are measuring normative growth, (i.e. students are being compared to their academic peers taking the same assessments), it is possible to calculate growth reliably. Student growth percentiles do not require identical tests or scales from year to year.

Can high scoring students still demonstrate growth?
Yes. Students that typically have high scores on state assessments will be compared to all other students in the state that also have high scores. The data show that even students that score at the top of the scale will have varied performance the next year, so the model allows us to identify growth for students at the upper end of the scale.

Which students get growth percentiles?
The students included in the student growth percentile calculations are those that attend public school and took a state assessment during the spring administration. Certain test types and categories of students are excluded from this comparison group. Only students that have at least two years of consecutive scores are included. For example, if a student has a score in 5th grade, but not in 6th grade, she would not be included in the analysis. Because of this requirement, student participating in the SBA field test in spring 2014 did not receive SGPS for the 2013-14 and 2014-15 school years.

All available scores are used in the model, as long as they are consecutive. Washington’s student growth percentiles are calculated using assessment data beginning in 2005-06. All students in the state that have valid and consecutive test scores in the same subject and grade form the norming population for the calculation of the SGPs.

Grade TestedMathReading/ELA

Although the table lists the testing grade of students that would receive a student growth percentile, these students are now most likely in the next higher grade. SGPs will not be calculated for Science, Writing, EOC Biology, or EOC Math.

How were SGPs for Math Year 1 and Year 2 end-of-course assessments calculated?
Prior to the 2014-15 school year, SGPs for the end-of-course assessments are calculated in a number of ways.
If a student took the EOC 1 in 7th, 8th, 9th or 10th grade, their MSP math score(s) from the previous year(s) were used to calculate growth. If a student took EOC 1 in 10th grade, their 8th grade MSP score was used.

If a student took the EOC 2 in 9th or 10th grade, and they took the EOC 1 in the previous year (8th or 9th grade, respectively), their SGP was calculated using the EOC 1 score as a prior, as well as any consecutive MSP Math scores previous to their EOC 1 score. If a student did not have an EOC 1 score in a previous year, and they did have an MSP Math score in 8th grade, this score was used and their 10th grade EOC 2 SGP represents two years of growth.

Students that take the EOC 1 and EOC 2 in the same testing window or the same school year, even if different semesters, did not receive an SGP that uses EOC 1 as a prior year score for the EOC 2.

How do we interpret a growth percentile in 10th grade Reading or Algebra, if there was no score in 9th grade?
Growth percentiles were calculated for subjects in 10th grade before the 2014-15 school year even though those students did not have a prior year score. SGPs for students who test in 10th grade are less straightforward, because of the 9th grade test gap and thus one must use caution when interpreting those scores. One needs to say “how did this student perform over the previous TWO years, relative to academic peers using 8th grade and prior scores”. Attributing 10th grade SGPs to a teacher is not recommended, but the information is useful in evaluating a student’s progress toward proficiency. With the change in the census test from 10th grade to 11th grade in 2015, SGPs for high school students are no longer calculated. These SGPs would represent growth over a three-year span, making the interpretation of them increasingly difficult.

What can student growth percentiles tell us?
Student growth percentiles are primarily a descriptive model, telling us what amount of growth a student has made over the last year. This growth model is not a value-added model; it does not attempt to separate a teacher or school effect on student learning. SGPs can, however, help answer the following questions (Yen, 2007):

Parent Questions:

  • Is my child growing adequately toward meeting state standards?
  • Is my child growing more or less in Math than Reading, relative to other students in the state that scored similarly?

Teacher Questions:

  • Did my students grow adequately toward meeting state standards?
  • How much growth do my students need to become proficient?
  • Are there students with unusually low growth who need special attention?

Administrator Questions:

  • Are our students growing adequately toward meeting state standards?
  • How does the growth of students in my school compare to students in other schools?
  • Are students in different grade levels within my school growing similarly?

What kind of data will districts receive and when?
Student growth percentiles have been calculated and provided for the four school years of 2010-11 through 2014-2015. The following documents have been made available to districts:

  • Individual student reports, including student growth percentiles charts for math and reading
  • School-level reports that show individual students’ growth percentiles; one report for each subject/grade combination
  • District-level reports that show the median growth percentile of each school
  • School growth summary reports
  • Excel data files that include SGPs at the student-level and aggregate data at the school, district, and student group levels

Download examples of these reports.

Where can districts find the data?
Districts will receive electronic versions of SGP reports. These reports and excel files will be available to districts in the Washington Assessment Management System (WAMS) accessed through the EDS portal. District assessment coordinators can download the data by clicking on ‘Profile’, then ‘File Downloads’.

Will student growth percentiles be reported publicly?
OSPI reports student subgroup, school and district-level median student growth percentiles publicly on the  OSPI State Longitudinal Data System (SLDS) K-12 Data & Reports website. The data is available visually under the “Student Growth” tab on the K12 Data and Reports (SLDS) page. The data are also available for download under “Static Data Files”. Click on the “Assessment” menu item then scroll down to find the SGP files and reports. New data for the 2015-16 school year will be available in October.

Why are Washington school districts not required to distribute student growth reports to students and families?
It is at the discretion of Washington school districts whether or not to distribute student growth reports to families and students. OSPI views the distribution of individual SGP reports as optional at this time for several reasons. OSPI recognizes that the model is complex. OSPI’s intention is to allow districts time to understand the data and to provide professional development to school administrators and educators. We know this takes time and effort, and given other competing initiatives (e.g. Common Core State Standards and the transition to the Smarter Balanced Assessment), we recognize it is challenging to also roll out a metric with new reports. In addition, there is a gap in the availability of SGP data for schools that administer the Smarter Balanced field test in the spring of 2014 due to students not receiving individual test results. For these districts, investing the necessary time and energy into training on SGPs may be a lower priority.

How will the student growth percentile data be used?
The State Board of Education’s Achievement Index School median student growth percentiles are one of the new measures in the revised State Board of Education’s Achievement Index. For more information, please view this short summary video developed by the SBE that summarizes changes to the index as well the current status. Please visit the SBE Achievement and Accountability Workgroup’s (AAW) webpage to view the index design documents that demonstrate how SGPs, proficiency and college and career readiness are used to determine a school’s index rating.
Teacher Principal Evaluation Project (TPEP) Districts may eventually choose to use student growth percentiles as a component in teacher evaluation. SGPs could inform teacher evaluations if schools attribute individual students to specific teachers. OSPI recommends waiting until the 2016-17 school year to include SGPs in the mix of student growth measures used in the evaluation of performance, at which point Washington schools will have had time to adjust to new standards and assessments. For more details on the use of student growth percentiles in teacher evaluation, please see the TPEP Statement on Student Growth Percentiles. More information on this topic will be available by visiting the TPEP Web site.

Where did student growth percentiles originate?
Washington State student growth percentiles were developed by Damian Betebenner of the Center for Assessment (NCIEA). They were first developed in Colorado for use in their Accountability framework in 2007.

Where can I get more information?
Please visit the Student Growth District and School Resources webpage for additional videos and materials.

OSPI is very interested in hearing your questions, recognizing student growth percentiles are a complex method of assessing student growth percentiles. We look forward to continued communication. Please email your questions and feedback to

What is the difference between baseline- and cohort-referenced SGPs?
SGPs for the 2013-14 school year used a different methodology (baseline-referenced SGPs) than earlier years and the 2014-15 school year (cohort-referenced SGPs). In 2013-14, approximately 30 percent of Washington students participated in the Smarter Balanced field test and did not receive valid test scores. Since selection into the field test was not random, the pool of academic peers in the same year was potentially biased. To avoid this potential bias, baseline SGPs were introduced. With the baseline method, a student’s academic peers include Washington students from past years. In other words, the most recent or current cohort is compared to previous cohort(s). Due to the change in tests, the only potential comparison for students in the 2014-15 school year was academic peers using the Smarter Balanced test. Hence, OSPI returned to calculating cohort-referenced SGPs where students are compared to their academic peers in the same year.

The cohort-referenced SGPs differ in interpretation from baseline SGPs. For example, if Anthony, a 5th grader in 2015, has an SGP of 65 using the cohort method we would interpret his score this way: Anthony has performed better than 65% of his academic peers, where his academic peers are students in 5th grade in 2015 who have at least two years of scores. Anthony’s baseline SGP of 65 still means that he scored better than 65% of his academic peers, however, his academic peers also include 5th graders from past years.

How do statewide medians differ under the baseline and cohort method for calculating SGPs?
The cohort method of calculating SGPs results in a state median of 50 for any subject and grade combination because the norms are established using student scores from only the current year. In this scenario, half of the state’s students have growth below 50 and half above. In contrast, the state baseline-referenced median SGP is not necessarily 50 since it depends on how students in that year performed relative to students in previous years. A median that is greater than 50 indicates that the most recent cohort of students performed better relative to previous years of students and vice versa. Since the baseline method was only used to calculate SGPs for the 2013-2014 school year, statewide medians will only differ from 50 in that year. To see those results, please refer to the Guide to SGP Files on WAMS (2013-14).

How is growth calculated for students obtaining the Highest Obtainable Scale Score (HOSS) on the Smarter Balanced Assessment?
For the 2014-15 school year, students scoring at HOSS received an SGP of 99.

Are SGPs available for students that took the SBA field test in 2013-14?
Student growth percentiles require at least two consecutive years of valid scores. Since students that took the field test in spring 2014 did not receive scores, they did not receive SGPs for the 2013-14 and 2014-15 school years. However, those students will receive SGPs for the 2015-16 school year.

How are SGPs calculated for the first year of a new assessment, as happened in 2014-15 with the transition to Smarter Balanced?
SGPs measure normative growth so students are compared to their academic peers taking the same assessments. Growth is not being calculated relative to individual performance on a test; it’s calculated relative to how a student’s academic peers performed. A student’s academic peers represent all students in Washington in the same grade and assessment subject that have followed a similar assessment score path. Because of this, SGPs do not require the same test or identical scales from year to year.



   Updated 6/6/2016

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