A report on student testing released Thursday finds big gaps in most states between the percentage of students shown to be proficient in reading and math on state tests and the much lower number found to be proficient on a national benchmark test.

Georgia, Texas and South Carolina and dozens of other states showed significant gaps between their state tests in the 2013-14 school year and the results of the National Assessment of Educational Progress on tests of reading and math in fourth and eighth grades.

“Too many states are not leveling with students or parents. They’re being told students are proficient, but by external benchmarks they’re not prepared at all,” said Michael Cohen, the president of Achieve, the education reform group that conducted the survey. Cohen added that improvements are expected with the new tests.

Many states adopted new tests to measure the new standards. Cohen called it a “multi-year, multi-state effort to raise expectations.”

Georgia, for example, began its new Georgia Milestone tests this year. The state had some of the biggest gaps that Achieve found on last year’s tests: 60 percent more scoring proficient in fourth-grade reading on the state test than on national assessment; a 43 percent gap on fourth-grade math; a 65 percent gap on eighth-grade reading; and a 53 percent gap on eighth-grade math.

The report also found some states had a narrow gap. For example, in eighth-grade math, 14 states showed their state proficiency levels differed from the national assessment by 15 percentage points or fewer. Two states had higher scores on their state tests than on the national benchmark test: New York, 10 points higher, and Massachusetts, 3.

The others, which had higher state scores by 15 percentage points or fewer, were Utah, Michigan, North Carolina, Wisconsin, Nevada, Alabama, Colorado, Minnesota, Wyoming, Washington, Kentucky and West Virginia.

The National Assessment of Educational Progress, sometimes known as the “nation’s report card,” is the only consistently used national measure of all students. It is given every other year to a sample population.

Achieve’s report found that more than half the states had a gap of 30 percentage points or more between the higher percentages of students scoring proficient on state tests compared with the lower number hitting what the national assessment tests deem as proficient in 2013-14. It called the discrepancy an “honesty gap.”

“This is a time to stay the course even in the face of political pressures we know are out there,” he said, a reference to social conservatives’ opposition to the Common Core.

Opponents view the new standards as an example of federal overreach. They were developed by state governors and school officials, but the Education Department encouraged states to adopt them by making higher standards part of the qualifications for competitive grants.