AUGUSTA — The Maine Department of Education will suspend the A-F school grading system this year because students are taking a new assessment test and the state will not have enough data to measure their progress, education officials said Monday.

Students in Maine schools will begin taking the new assessment test – called Smarter Balanced – in March, and officials said it would not be possible to measure students’ year-over-year growth using two different tests.

The next round of report cards will be issued in the fall of 2016, after students have taken the new Smarter Balanced tests for two years, acting Education Commissioner Tom Desjardin said in a memo to school officials.

“Instead, performance on the new assessment this spring, which will be made available on our public Data Warehouse, will establish a new benchmark,” he wrote. “It will only be in the fall of 2016 when we have two years of student achievement data that we will again be able to measure how schools are doing and release the next round of report cards.”

The grading system, which gives individual schools grades from A to F based on several factors – such as test scores, graduation rates and improvement in scores – was implemented in 2013 under Republican Gov. Paul LePage and designed to bring transparency and accountability to the state’s public school system.

The A-F system has been a hallmark of the governor’s education reform efforts. It has drawn support from those who say the grades are a way to let parents gauge how well their children’s schools are performing, but also criticism from those who say it stigmatizes poor districts and is not an accurate assessment of the quality of a school.

School officials say the move to suspend the grades for a year makes sense.

“The state early on acknowledged that it would be impossible to compare the results” of the two tests, said Lewiston Superintendent Bill Webster. “They weren’t even going to try.”

Webster and some other superintendents have come out against the report cards, saying that low grades penalize districts with a large number of low-income students.

“Be that as it may, we have another year” before the next round of grades come out, Webster said.

The Maine Education Association, which is opposed to the report cards in general, said the suspension was necessary.

Comparing the results of two different tests, MEA President Lois Kilby-Chesley said, would be like comparing apples and oranges.

The MEA has consistently opposed the A-F grading system since it was introduced.

“The Maine Education Association continues to believe the A-F grading system is based on socio-economics and tells us nothing about a school’s performance,” Kilby-Chesley said in an email. “However, if the Governor wishes for punitive school grading to continue, it only makes sense this year is exempt because comparing the student scores from last year’s New England Comprehensive Assessment to this year’s new Smarter Balanced designed test would be like comparing apples to oranges and would provide no significant information or data.”

Report cards released last year showed that about 28 percent of schools received lower grades in 2014 than the year before, and two dozen more received failing grades.

Experts have warned that scores are likely to drop using the new tests, which are based on the Common Core standards. Those standards spell out exactly what students in each grade level are expected to know, such as the coordinate system in fifth-grade math.

Maine schools began teaching those Common Core standards last fall. Most districts have been holding parent nights to explain the new Smarter Balanced tests, which will be given for the first time next month.

Based on other states’ experiences, it’s almost certain test scores will drop initially, and parents and students will have a rough transition.

In Kentucky, the first state to administer Common Core-based tests, there was a 30 percent to 40 percent drop in proficiency in reading and math, according to results released in late 2012.

Rep. Sara Gideon, D-Freeport, has introduced a bill that would require school districts to notify parents that they have the right to opt out of the Smarter Balanced test.

The effort is part of a broader movement in other states against standardized testing.

Although officials acknowledge that parents already have the right to opt out, the No Child Left Behind law requires schools to test at least 95 percent of students each year, so if too many opt out, the school could be considered a failing school even if test scores are high.

The tests, and the materials used to teach Common Core, emphasize critical thinking skills as opposed to rote memorization. For example, instead of reciting multiplication tables, students must explain the process of how they arrived at a correct answer to a math question. Instead of a vocabulary test, they must explain what motivated an author to write a book a certain way.