Fair Evaluations for Teachers: Exploring Growth vs. Absolute Measures of Student Achievement

Since Governor Malloy released Senate Bill 24, we have noticed a lot of anxiety over the idea that teacher evaluations will be partly informed by standardized tests.  S.B. 24 relies upon the teacher evaluation guidelines that were unanimously approved by the Performance Evaluation Advisory Council (PEAC), which calls for 22.5% of a teacher’s evaluation to be based on standardized testing.

Anxiety over being evaluated on the performance of students who might already be behind is a valid concern, but there is a model for using standardized testing to evaluate teachers fairly. You see, there is a difference between measuring student learning against an absolute performance standard and measuring growth-based performance (which measures each student’s growth against his or her own baseline).  While the details about the proposed evaluation model are still being worked out, we wanted to take a minute to talk about what we mean when we say “growth-based” student performance measures – because we know this phrase isn’t very clear and can be alarming.

Measuring student learning based on “growth” means that each student’s performance is measured against his or her own historical performance and the historical performance of a similar peer group, so that a predicted performance “growth” rate can be set for each student.  Then, each student’s actual growth in learning is compared with the expected performance that was determined for him or her.

Essentially, annual growth measures are determined by comparing groups of students with similar characteristics and starting points, and measuring each student’s progress relative to his or her own starting point.  According to the U.S. Department of Education definitions,  “effective” teachers will have students who demonstrate at least one grade level of academic growth, every year. So HOW can “growth” be measured fairly? (This article by The Education Trust does a good job explaining it.) Basically, if you wanted to set annual growth goals for a single student, let’s say his name is Michael, you would use data on Michael’s past performance and the past performance of students with similar characteristics to Michael (for example, third grade, low-income students).  You would use this information to set expectations for Michael’s academic growth.  Under this model, an effective teacher would help Michael to learn and demonstrate at least one year of academic growth during one school year.  Again, using the U.S. Department of Education’s definitions, a highly effective teacher would help his or her students to achieve high rates of student growth by exceeding the predicted academic growth for one school year.

It’s important to recognize that a “growth” based model treats teachers fairly and does not blame or penalize teachers for teaching students who may start out behind or have diverse learning needs.  In fact, these are the very factors that are taken into consideration when determining academic growth measures for students. It’s also important to remember that under the PEAC guidelines student achievement, as measured by a standardized test, counts for 22.5% of a teacher’s evaluation, with other measures of student learning, professional practice and professional activities comprising the majority of the evaluation.

A number of states, such as Tennessee, Louisiana and Colorado have adopted or implemented similar “growth” based systems to determine a teacher’s impact on student achievement.  We think you would agree that it is reasonable to expect that students be able to demonstrate one year of learning and growth for every year they are in school.  Similarly, we think you would agree that teachers need to be able to help students learn so that all students make at least one year of growth, every year.