By Alexandra Usher and Nancy Kober, Special to CNN

Editor’s note: Alexandra Usher is a senior research assistant at the Center on Education Policy at The George Washington University's Graduate School of Education and Human Development. Nancy Kober is a consultant to the Center. They co-authored the report, “Student Motivation—An Overlooked Piece of School Reform."

(CNN) – We’re taking many steps as a nation to boost student achievement. We’re raising academic standards, revising curricula, revamping low-performing schools and improving teaching and school leadership.

These are all critical elements of school reform, but what often gets the most attention are the tests we’ve put in place to make judgments about schools, teachers, principals and students. These tests are intended to measure how well students are learning and teachers are teaching. They are also supposed to motivate students to study harder.

Student motivation is an important ingredient in school reform, and one that is often overlooked in policy debates. Even with strong accountability, a well-designed curriculum and good teaching, it is difficult to raise achievement for students who lack motivation. But are tests really good motivators?

To draw greater attention to the role of student motivation, the Center on Education Policy has released a series of papers summarizing findings from studies by psychologists, sociologists and other experts. One of these papers looks at research on tests as motivational tools for students - and the findings suggest we have too much faith that all tests will motivate all students.

The same student might be motivated to different degrees depending on the test, the stakes attached to test results, the subject matter and many other factors. The term “high-stakes” testing often brings to mind the standardized state tests used for accountability. But teacher-designed classroom tests may be more effective at motivating students than state tests if the classroom tests have a direct effect on students’ grades.

Even among standardized tests, the stakes and the level of motivation vary. State tests that are used to determine graduation status and grade promotion matter greatly to students and can be motivators for many students. State tests that don’t count toward graduation but are used for school and district accountability can be somewhat motivating for students because they have consequences for educators, who pass along this pressure to students. The National Assessment of Educational Progress, which is used to track nationwide trends in achievement, has virtually no consequences for individual students or teachers and is often considered a “low-stakes” test.

Psychologist Carol Dweck points out that if the goal of education is to produce creative and innovative learners, then the tests typically used for accountability may work against this goal by signaling to students that intelligence is fixed and unchangeable rather than something that can grow with effort.

Similarly, tests that emphasize reaching a specific performance benchmark can undermine motivation by invoking anxiety, frustration and fear of failure in students who feel that meeting the benchmark is beyond their abilities, according to research by Kennon Sheldon and Bruce Biddle.

Moreover, several studies have noted that some of the practices used to prepare students for high-stakes assessments - such as excessively drilling students or eliminating interesting topics and activities to make more time to teach tested material - can decrease students’ interest and motivation.

In other words, despite the best of intentions, some types of tests can stifle motivation for some students.

Yet many students are motivated to work harder by the consequences attached to high-stakes tests. When faced with a test to determine grade promotion, the majority of students in Chicago responded by paying more attention to class work and increasing their efforts, according to a study by Melissa Roderick and Mimi Engel. The concern, however, is what to do for students who respond to testing by becoming resentful and losing confidence.

In general, the studies we reviewed suggest that assessments that reward growth, effort, and strategizing have a stronger motivational effect than those that emphasize competition or reward a fixed level of performance.

More frequent assessments with goals that start easy and gradually increase in difficulty can build students’ academic competence and sense of control, as can opportunities for students to demonstrate their knowledge with performance tasks or low-stakes tests before taking an assessment that counts. Students also need to understand what steps they must take to succeed on a test and must have sufficient opportunity to prepare for it.

Finally, like any motivational tool, assessments have the strongest power to motivate when their goals are not too difficult or too easy and when they align with students’ own personal interests and goals.

The opinions expressed in this commentary are solely those of Alexandra Usher and Nancy Kober.