Massachusetts is the latest battlefield over the question of how to evaluate teachers. At the center of the conflict is the favorite idea of Arne Duncan and Bill Gates: evaluating teachers by the test scores of their students (or if not their students, someone else’s students). The new Every Student Succeeds Act relieved states of the obligation to tie teacher evaluations to students scores. Oklahoma and Hawaii recently dropped the measure, which many researchers consider invalid and unreliable.

The state plans to impose its evaluation system on all teachers, including teachers of the arts and physical education. How the state will measure the students’ growth in music or art or sports is not clear.

Researchers at the University of Massachusetts-Amherst studied the plan and criticized it:

A 2014 report by the Center for Educational Assessment at the University of Massachusetts Amherst, which examined student growth percentiles, found the “amount of random error was substantial.”

“You might as well flip a coin,” Stephen Sireci, one of the report’s authors and a UMass professor at the Center for Educational Assessment, said in an interview. “Our research indicates that student growth percentiles are unreliable and should not be used in teacher evaluations. We see a lot of students being misclassified at the classroom level.”

The Massachusetts Teachers Association, the largest teachers’ union in the state, has come out in opposition to the plan, as has the Massachusetts Association of School Committees, representing the state’s elected school board.

But state officials, led by state Commissioner Mitchell Chester, insist that they won’t back down. Boston’s superintendent, Tommy Chang, a graduate of the unaccredited Broad Superintendents Academy, is acting to implement the evaluations.

A centerpiece of Massachusetts’ effort to evaluate the performance of educators is facing mounting opposition from the state’s teacher unions as well as a growing number of school committees and superintendents.

At issue is the state’s edict to measure — based largely on test scores — how much students have learned in a given year.

The opposition is flaring as districts have fallen behind a state deadline to create a “student impact rating,” which would assign a numeric value to test score growth by classroom and school. The rating is intended to determine whether teachers or administrators are effectively boosting student achievement. The requirement — still being implemented — would apply to all educators, including music, art, and gym teachers.

“In theory it sounded like a good idea, but in practice it turned out to be insurmountable task,” said Glenn Koocher, executive director of the Massachusetts Association of School Committees. “How do you measure a music teacher’s impact on a student’s proficiency in music? How do you measure a guidance counselor’s impact on student achievement?”

Critics question whether the data can be affected by other factors, including highly engaged parents or classrooms with disproportionate numbers of students with disabilities or other learning barriers. The requirement has also created problems in developing assessments for subjects where standardized tests are not given, such as in art and gym.

Resistance has escalated in recent weeks. On Thursday, the state’s largest teachers union, the Massachusetts Teachers Association, as well as others successfully lobbied the Senate to approve an amendment to the state budget that would no longer require student impact ratings in job evaluations. A week earlier, the Massachusetts Association of School Committees passed a policy statement urging the state to scrap the student impact ratings.

But some educators see value in the student impact ratings. Mitchell Chester, state commissioner for elementary and secondary education, defended the requirement, which has been more than five years in the making.

Commissioner Chester is deeply involved with the Common Core and the tests for Common Core. Until recently, he was chair of the PARCC Governing Board.

The educational turmoil in Massachusetts is baffling. It is the nation’s highest-scoring state on standardized tests, yet school leaders like Mitchell Chester can’t stop messing with success. Although they like to say they are “trying to close the achievement gap” or they are imposing tougher measures “to help minority students,” these are the children who fall even farther behind because of the new tests, which are harder than past tests, and are developmentally inappropriate, according to teachers who have seen them.

What is happening in Massachusetts is the epitome of “reform” arrogance. Why doesn’t Commissioner Chester support the fine teachers he has and fight for better funding and smaller classes in hard-pressed urban districts like Boston?