Thousands of additional students in Montgomery County are getting A’s in key high school classes, an apparent case of grade inflation in Maryland’s largest school system that follows major changes in how students are evaluated.

New data show the percentage of A’s across core math courses nearly doubled from the first semester of 2014-2015 to last school year, rising from 16 percent to almost 32 percent. B’s rose more modestly while C’s, D’s and E’s dipped.

Similarly, more students got A’s in English, science and Advanced Placement courses, in a profusion of high marks that is stirring concerns that students and parents may be getting a false sense of proficiency. Some educators and parents place blame on that significant policy shift two years ago.

“It is grade inflation. I don’t know how you frame it any other way,” said Christopher Lloyd, president of the Montgomery County Education Association, the teachers union. “I don’t think the grades in high school classes shift like that. The shift was really around this change in policy and in how grades are computed.”

The surge of A’s follows a controversial decision in 2015 to end a longtime practice of giving final exams in high school courses in the county. That move came amid a national outcry over too much testing. As Montgomery scrapped its finals, it also changed how grades are calculated.

Two school years later, the numbers suggest that getting A’s is easier than it once was in one of the nation’s largest school systems. Some of the data were posted by the school system, following a school board member’s request, and some were obtained through a public records request filed by The Washington Post.

“I’d love to think we’re twice as good and students are learning twice as much,” said Leah Wilson, chair of the English department at Richard Montgomery High School in Rockville. “But when I look at those numbers, I see the policy at work.”

Under the revised approach, semester grades are determined through a “quality points” method that averages a student’s two quarter grades — and rounds up in most cases. An A in one quarter and a B for the next would mean an A as a final semester grade. And a B-C combination would produce a semester grade of B.

Previously, final exam grades were factored in. But if classes had no exam, the semester grade was based on the trend that prevailed: If a student got an A the first quarter during that semester but a B during the second quarter, then the semester grade was a B.

School system officials said they are monitoring the data and suspect multiple factors may explain the spike in A’s.

“The jury’s still out to some degree because it’s only two years of data,” said Scott Murphy, director of secondary curriculum and districtwide programs for the Montgomery County school system.

Murphy pointed to “changing conditions” as the school system ended two-hour final exams each semester and switched to a system of quarterly assessments in 2016-2017. The idea was that shorter, more frequent looks at student progress would reduce the testing burden, leave more time for learning and give teachers more useful information.

“Certainly, grading calculations are playing into the increase of A’s, but there are multiple variables and changing conditions and it’s hard to point to a single root cause,” he said.

Murphy underscored that every grading system has flaws and drawbacks. The school system had considered four options when it made the switch. “There’s no perfect science to grading,” he said.

Others found the sudden explosion of A’s disconcerting.

“It is shocking because we’re not seeing a lot more indicators that our children are more proficient than they were two years ago,” said Cynthia Simonson, vice president for educational issues with Montgomery’s countywide council of PTAs.

If students were making other major gains — on SAT, AP or state test scores — it would be heartening to see so many A’s, Simonson said. “We would celebrate,” she said.

But when A’s suggest grade inflation, she wonders how colleges will view student transcripts. And she worries about effects on students.

“I’m concerned about the student who believes they’re mastering the material, continues on and then faces the realization they are not prepared,” she said.

The spike in A’s came to wider attention after Jill Ortman-Fouse, a school board member, asked for data on grades, following complaints from teachers and principals about how the grading change was playing out.

The educators said student effort was slipping in the latter half of each semester as students believed their grades were locked in, she said.

“I want to make sure our students are taking full advantage of our courses and getting the full benefit of the learning,” Ortman-Fouse said, adding that she plans to ask for quarterly data to better understand what is happening.

The data the district provided looked at math, English and science grades, by semester, for two years before the grading shift changed and two years after.

The share of English grades across eight courses that were A’s for first semester in 2014-2015 — 21.4 percent — jumped to 38.7 percent by last school year, an 81 percent increase. For second-semester English, the increase was 57 percent.

Likewise, the increase across eight first-semester math courses was 98 percent for first semester and 85 percent for second semester. Across nine science courses, A’s were up roughly 50 percent each semester.

Math gains may be especially notable: For years, thousands of high school students in Montgomery failed their final exams in math.

Many teachers had expected the grading change to trigger higher marks, said Lloyd, the president of the county teachers union. He said many teachers would like to see final exams brought back, along with the district’s previous grading system.

Lloyd said it is important to get grades right so that students and families have a strong understanding of academic progress, and colleges and employers can rely on the marks.

“There are expectations in our society from colleges and employers about what grades mean,” he said.

The issue needs more examination, said Glenn Miller, a biology teacher at Sherwood High School, who said he sees the issue as an educator and a father.

“As a parent, I want to make sure I know exactly what a grade means, and exactly where I need to intervene and help my child,” he said.

Other parents caution against changes that will make school more stressful.

Data on a sampling of three AP courses requested by The Post showed significant improvements from the year before the grading switch to the year after.

Patricia O’Neill, a school board member, said the rise of A’s is concerning but still unclear.

“At first blush, it might look like grade inflation,” she said, “but was our previous grading standard wrong? Obviously, we have to dig into this and look at what is the true meaning of an A.”

Ned Johnson, president of PrepMatters, a college advising, tutoring and test preparation company in Bethesda, McLean and the District, said he has noticed more parents asking about the disconnect between stellar grade-point averages and lower-than-expected SAT scores.

One result of the expanding number of A’s, he said, may be that admissions tests such as the SAT and ACT are more important in college applications — a trend that would cut against a move by some colleges and universities to go test-optional.

“If there is less specificity in grades, colleges have to lean more on other measurements,” he said.