The Little-Known Statistician Who Taught Us to Measure Teachersby Kevin Carey
May 19, 2017
NY Times
This article summarizes the work of Dr. William S. Sanders, statistician (April 26, 1942 - March 16, 2017) known for developing the controversial value-added method of evaluating teacher effectiveness.
Imagine two students. Both start the year at the same level in math, and both improve by 15 percent. But in previous years, the first student had been improving slowly, by 5 percent annually. For him, 15 percent is a big gain. But the second student had been improving by 30 percent per year. For her, 15 percent is a troublesome slowing down.
To fairly evaluate teachers, Mr. Sanders argued, the state needed to calculate an expected growth trajectory for each student in each subject, based on past test performance, then compare those predictions with their actual growth. Outside-of-school factors like talent, wealth and home life were thus baked into each student’s expected growth.
This value-added method of teacher evaluation, focused on each individual student's year-over-year growth, seems to support appropriate challenge (teaching in a child's zone of proximal development or ZPD)... it does not seem to value or reward closing achievement gaps or excellence gaps by capping the growth of students at the top.
it didn’t support the tenure and credentials system
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Schools were collectively spending billions to give teachers with master’s degrees extra pay. Yet their value-added bell curve looked little different from the curve for teachers without those degrees. Nor did effectiveness grow in lock step with years of service
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The Common Core standardized tests, already disliked by opponents of federal power on the right, also gained critics on the left, who objected to their use in evaluating teachers
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scores for individual teachers can change significantly from year to year. But this variance exists in part because teachers are sometimes much more effective with one group of students in one year than another in the next
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evaluation systems... ultimately leaned more heavily on structured, in-person observations of teacher practice. Unlike value-added ratings, observations can provide diagnosis along with evaluation, showing teachers not just how they’re doing, but how to improve.
Just as students are individuals, teachers are individuals. Everyone benefits when there is continual feedback and adjustment, focused on striving to find the optimal student-teacher "fit".
A linked article in Education week shares:
"Sanders stood for a hopeful view that teacher effectiveness dwarfs all other factors as a predictor of student academic growth," his family wrote in his obituary. "His position challenged decades of assumptions that student family life, income, or ethnicity has more effect on student learning. Sanders believed, simply put, that educational influence matters and teachers matter most."
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Effective teachers, he says, "get excellent gains across the entire spectrum of kids in their classroom [because] they've got kids working at different paces and at different places." Ineffective teachers, on the other hand, "tend to focus on the lower-end kids. They may be sincere and conscientious, but they're holding back the others."
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His research found that three consecutive years of ineffective teachers can significantly hamper a child's learning over the long run.
Some teacher evaluation methods may be more popular or readily accepted under different educational climates. There is good and bad in everything.
Ultimately, Dr. Sanders developed one more tool... no tool can do every task, but it is helpful to have a wide variety of tools available.
