Tennessee’s overhaul of its system for evaluating teachers has coincided with real and measurable benefits for students and teachers alike, says an analysis released Thursday by the National Council on Teacher Quality.

The controversial changes — which since 2011 have required more frequent and rigorous evaluations aligned to student outcomes — have rankled teachers but also made a difference when it comes to teacher retention and students’ academic growth, according to the research and policy group, which backs extensive reforms to teacher preparation and evaluation.

Teachers earning highly effective ratings are generally being retained at a higher rate than less effective teachers across Tennessee. An increasing number of districts logged the highest levels of student growth on state assessments during three school years ending in the spring of 2017. And a recent survey found that 72 percent of educators believe the evaluation process has improved their teaching, up from 38 percent in 2012.

However, other research paints a much less encouraging picture of evaluation reforms, particularly a recent study commissioned by the Gates Foundation that showed few gains in student achievement under the extensive changes, including in Tennessee’s largest district in Shelby County.

The newest analysis spotlights Tennessee as one of six places that are pioneering evaluation systems aimed at improving the quality of teaching. The others are New Mexico and districts in Dallas, Denver, the District of Columbia, and Newark, New Jersey.

All six use both student test scores and classroom observations to evaluate all of their teachers every year, giving significant weight to student learning. They also feature at least three rating categories, a big change from the days when teachers were assessed as either satisfactory or unsatisfactory, with almost all earning the former rating.

Perhaps most significantly, each of the systems highlighted in the analysis link evaluation results to opportunities to earn higher pay. In Tennessee, districts are now required to differentiate compensation based on educator ratings or one of two other criteria: additional roles and responsibilities, or serving in hard-to-staff schools or subject areas.

The changes have happened in the decade since the National Council on Teacher Quality analyzed state and local regulations affecting teachers and called out evaluation policies across America as broken, counterproductive, and badly in need of an overhaul.

Not surprisingly, the switch to new systems has been hard.

In Tennessee, educators found the revamped evaluation model cumbersome, confusing, and opaque after its launch was rushed to help the state win a $500 million federal award in 2010. That feedback contributed to ongoing tweaks to teacher training and evaluation systems, outlined in another new report from FutureEd, a second policy think tank favoring evaluation reforms.

“None of these systems were perfect out of the gate,” said Kate Walsh, president of the National Council on Teacher Quality, the group behind this week’s analysis. “System leaders recognized this and worked continuously to enhance system design, implementation, and use.”

But the backlash continues to bubble up in Tennessee, especially as the state’s messy transition to a computerized assessment has undermined the credibility of student test scores and prompted a recent legislative order to mostly disregard this year’s results in evaluations.

Last April, the testing problems overshadowed another study by Brown University researchers who reported that Tennessee teachers are showing substantial, career-long improvement under the state’s reforms. The finding was important because of some previous research that teacher improvement is relatively fixed, with most development coming in the first three to five years of a teacher’s career and then plateauing.

Despite the upbeat assessments in the NCTQ, Brown, and FutureEd reports, the future of Tennessee’s teacher evaluation system — which is now fully integrated into other systems for teacher preparation, licensure, support, and dismissal — is uncertain due to testing headaches that call into question the evaluation’s accuracy and fairness. The Gates study, which also found that low-income Memphis students didn’t necessarily get more access to effective teachers under evaluation reforms, hasn’t helped.

Outgoing Republican Gov. Bill Haslam has championed the reforms started by his Democratic predecessor and is urging the next administration to stay the course. His education chief says the latest analysis is a testament to the importance of incorporating student achievement into teacher ratings.

“Our evaluation model has developed the capacity of teachers to improve, put student growth at the center of our work, and established an expectation of continuous improvement,” Commissioner Candice McQueen said in a statement. “Even better, it’s working.”