Teacher evaluations spur some of the liveliest conversations in education reform. Should the performance of a teacher's students be considered? Should a balance be struck between experience and effectiveness? Perhaps most importantly: should teachers be paid based on how well they are evaluated?

This week, the National Council on Teacher Quality, a non-profit organization that advocates for reform of teacher policies, released a report detailing what kind of teacher evaluation policies states have adopted. The study was funded by the Bill and Melinda Gates Foundation and the Joyce Foundation.

In general, the report found that more states are moving toward more stringent teacher evaluations that incorporate student performance. In the last three years, 32 states have made some change to their teacher evaluation policies. More states are holding annual evaluations of teachers and more states added student achievement, such as their scores on state tests, as a critical element of their evaluation criteria.

In the report's conclusion, NCTQ outlined a long list of lessons to be drawn from these findings. Here are a few:

Teacher effectiveness measures don't have to be perfect to be useful. State review and approval of district evaluations may not be an adequate approach to ensuring quality and rigor. Designing measures of student growth for non-tested grades and subjects is an important challenge facing states. States shouldn't lose sight of the importance of classroom observations. Teacher evaluation policy should reflect the purpose of helping all teachers improve, not just low-performers. A number of factors have contributed to this trend, Daniela Fairchild, policy analyst at the Fordham Institute, a reform-focused education policy think tank, tells Governing. For starters, there is increasing evidence that teachers have the biggest impact on the progress and success of students. And an influx of "education governors," such as Indiana's Mitch Daniels and Michigan's Rick Snyder, have taken office and made education a focal point of their administrations.

"With the current economic situation, more states and districts are looking with a discerning eye at their teaching staff to make sure they're getting the best bang for their buck," Fairchild says, noting that teacher salaries often make up to 80 percent of a school district's budget. "It's not quite as easy to hide less effective teachers in classrooms now. It's not quite as easy to rationalize keeping them around."

So figuring out the best means of assessing teacher performance, particularly when it concerns high-stakes test results that have a financial impact for states and school districts, has become central to education reform. But, Dr. Andrea Dorrington, senior policy analyst for teacher quality at the National Education Association, tells Governing, policymakers should be cautious when applying value-added criteria, which often means student test scores, to their teacher evaluation policies.

Teachers should be involved in developing those policies, and metrics that quantify student growth, outside of their scores on tests, should be included, Dorrington says. For example, teachers could set learning objectives for their students and be graded on whether or not their students achieved them. Or students could take pre-tests and post-tests, which would indicate how they progressed throughout the year. Paired with student test scores, those criteria form a broader evaluation of how a teacher is performing than a system that focuses solely on the test results, she says.

"Teacher evaluations should be providing teachers with constructive and actionable feedback," Dorrington says. "Student achievement is often being interpreted by one group of people differently than another group of people. Until we have a shared understanding of what it means to be an effective teacher... we will have a problem."

Better communication between administrators and educators about how specifically teachers will be evaluated could bridge some of the gaps between reformers and unions, Fairchild concurs. Value-added teacher evaluations are complicated. "Teachers don't understand them. Most people don't understand them," Fairchild says. Teachers would benefit from a well-explained list -- "These are the 10 things I need to do," as Fairchild puts it, a strategy that has been implemented as part of the District of Columbia's IMPACT assessment program.

What's clear to all involved, though, is that the conversation about teacher evaluation policies is one that's crucial to the continued effort to improve the nation's schools.

"There has been a sea change in the understanding of how important it is to have a strong teaching workforce," Cynthia Brown, vice president for education policy at the Center for American Progress, tells Governing. "I don't think we know what a perfect evaluation system looks like. There probably never will be one perfect system, but what's exciting is to see states and districts developing and monitoring their evaluation systems."