Questions also swirl around how to interpret the available data. Experts say it is difficult to isolate the effectiveness of one teacher from the effectiveness of other teachers or tutors who work with students. It is also hard to know the role that out-of-classroom factors, such as poverty, language ability and home environment, play in student performance.
Value-added measures — an evaluation model embraced in many states and the District — use a complex algorithm that attempts to account for such variables to isolate the teacher’s influence, boiling it down to a single score. Reports have shown that value-added measurements can produce unreliable results when applied to individual teachers.
“It’s very difficult to get a clean, precise metric,” said Linda Darling-Hammond, an education professor at Stanford University who has studied such systems.
Without a widely available growth measure, districts in Northern Virginia are asking teachers to illustrate student growth primarily by setting goals. At the beginning of the year, teachers and administrators review students’ performance and set specific targets for progress.
State guidelines say teachers must use reliable measures, but that could mean reading fluency tests for a special education teacher, abdominal fitness tests for a physical-education teacher, and end-of-unit tests for a math teacher.
To determine student progress, Mike Bonfadini, a seventh-grade math teacher at Bull Run Middle School in Gainesville, used results from pre-tests, post-tests and retests for different chapters or units, as well as quarterly benchmark tests.
The school’s new teacher evaluations include at least two classroom observations by administrators and measure six other standards — professional knowledge, instructional planning, instructional delivery, assessment of learning, learning environment, and professionalism.
In the end, Bonfadini was rated in the highest of four categories. He said he was already monitoring student progress but that the new evaluation made him report it more carefully.
At the end of the day, his job is the same, he said: “You make a rapport with the students and help them learn to the best of your ability.”