About 25,000 elementary and middle school students in Maryland public schools, who will take the new Common Core exams for a test-drive next month, have been excused by federal officials from also having to take the Maryland School Assessment.

No Child Left Behind, the main federal education law, requires states to test every student in math and reading in grades 3 through 8 and once in high school and to publicly report scores. In many states, the scores are used to reward or punish teachers and schools.

This year, Maryland is among 45 states and the District of Columbia that are implementing the Common Core, new academic standards designed to ensure that students across the country have a common set of skills and knowledge at each level from kindergarten through 12th grade.

Tests that measure how well students are learning the new standards are still being developed. Thirty-six states and the District have agreed to field-test Common Core standardized exams. Test designers will use the results to create final versions of the exams, which will be given next spring and will replace old state tests.

Five other states — Connecticut, Mississippi, Montana, South Dakota and Vermont — also have been excused by the federal government from “double testing.” Students in Maryland will take the MSA or the Common Core field test, but not both. An additional nine states are seeking similar permission.

William Reinhard, a spokesman for the Maryland State Department of Education, said that one grade in every elementary and middle school in the state will be given either the Common Core reading or math field test. Because a field test is not designed to be a reliable measure of student achievement, the federal government has said that Maryland does not have to use scores from those tests for accountability purposes.

Meanwhile, some lawmakers in Maryland are trying to stop the state from administering the MSA at all this spring. They say that the old state test does not measure what’s taught in the classroom under the Common Core and that the state is wasting days of testing and at least $7 million to give an outdated test. Legislation has been introduced in both the Maryland Senate and House, but neither bill has moved out of committee yet.

“If there’s a chance that we don’t have to put our kids through an extra week of testing that means nothing, I sure would like to give our kids a break,” said Sen. Nancy J. King (D-Montgomery), sponsor of a bill that would stop the state from giving the MSA.

The argument over what kind of test to give coincides with a raging national dispute over the Common Core standards themselves.

Supporters say the Common Core standards emphasize critical thinking and analytical skills, as opposed to rote learning, and will enable U.S. students to better compete in the global marketplace. Opponents include tea party activists, who say the new standards amount to a federal takeover of local education, and progressives, who bristle at the emphasis on testing. Some academics call the standards too weak; others say they are too demanding, particularly for young students.