July-August 2012
June 27, 2012

SGPs, MGPs? How they measure student growth

Author: Sylvia Saunders
Source: NYSUT United

Come mid-August, the State Education Department is planning to issue a growth measure score for grades 4-8 ELA and math teachers and their principals. It will be a number between zero and 20, using student data from 2010-11 and 2011-12 assessments. So, how did SED get that "growth" number and how will it fit into the new evaluation system? Here are some answers.

Q: What is growth?

A: Student growth is the change in student achievement performance over time. A student growth model answers the question: How much, on average, did students' performance change over time?

Q: How will SED measure growth?

A:The Student Growth Percentile (SGP) model is the method SED has chosen. The SGP calculation looks at how much a student grew academically from one year to the next in comparison to other students with similar academic histories — or "academic peers." The state-provided growth model is measuring student growth, not achievement. This distinction is important because it helps ensure that all educators have a chance to do well on these measures regardless of the characteristics of their students.

Q: How does the SGP model work?

A: The SGP model compares a student to similar students statewide who had the same prior test scores. It factors in a poverty index, as well as allowances for students with disability status and English language learners.

These SGPs work just like other percentiles, running from 1 to 99, and they tell you where a student stands in a distribution of students — or how many students they out-grew. If Student A's SGP is a 45, that means she performed better in the current year than 45 percent of similar students.

The individual SGP for each of a teacher's students is averaged to give each teacher a mean growth percentile, or MGP. To find the mean of SGPs, SED will add the scores up and divide by the total number of scores. What the mean growth tells us is that on average, if Teacher A's MGP is 51, that means her students performed better than 51 percent of similar students. A principal's performance is measured by finding the mean growth percentile for all students in the school.

Q: Who will not get an MGP?

A: If you're not a grade 4-8 ELA or math teacher, you will develop student learning objectives, or SLOs, to measure growth beginning in the 2012-13 school year. (Click here for a primer on SLOs.)

To count in a teacher or principal's MGP for 2011-12, students will need to have two consecutive years of test scores. In order for an educator to receive a growth score, he or she must have a minimum sample of 16 student scores in ELA or math. (Educators with fewer than 16 scores would develop SLOs.) Keep in mind, the minimum number is based on the number of scores, not unique students. A teacher could actually teach eight students in math and those same eight students in ELA and that would be 16 scores.

Q: How will the growth score count in evaluations?

A: It will count for up to 20 points of an educator's overall rating, but only if your district's Annual Professional Performance Review (APPR) is approved. It will be converted into a subcomponent rating — highly effective, effective, developing and ineffective — and factored into the overall composite score.