He was wide-eyed at first. Ten-year-old Max Krauze opened his report card on a recent summer day in his North Chevy Chase living room to find an array of grades that reflected his fifth-grade work in Montgomery County’s public schools.

But Max lost interest quickly. Most of his grades were “P” — for proficient. By his count, he had 73 P’s spread across his four marking periods. “P is the only thing you get,” he said, noting just a handful of higher grades as he offered the report card to his mother. She quickly scanned the line of P’s.

“What does that tell me about him?” she asked. “What does that mean? He’s anywhere from average to excellent in a bunch of subjects.”

Max’s report card reflects a continuing shift in how Montgomery County is reporting grades for elementary school students. Gone are the traditional markers of A, B and C. Now there’s ES for exceptional work, P for proficient, I for in-progress and N for little or no progress.

It’s a change that comes as standards-based report cards are on the rise. At a time when school systems across the country have adopted standards-based curriculums and assessments, “grading practices are being seen as the next step,” said Thomas Guskey, a professor at the University of Kentucky who has done extensive research on grading.

Montgomery officials say their standards-based grading system provides a more detailed picture of student performance. But many parents say the report cards are difficult to decipher and leave them wondering how their students are really doing in class.

Maryland’s largest school system plans to take a closer look at the report card’s effectiveness, officials said. Montgomery’s new report card was used for the first time district-wide from kindergarten through fifth grade during the most recent school year.

“We will do more formal evaluations or focus groups to evaluate and hear from all of the stakeholders, including parents, about how it’s going,” said Niki Hazel, director of the elementary curriculum team for Montgomery schools.

Intended to reflect Montgomery’s more rigorous Curriculum 2.0, which is based on the national Common Core State Standards, the report card breaks down such broad topics as writing into categories: narrative writing, opinion writing, language use. The general idea is to give a fuller view of performance and progress.

“To me, it provides a lot more clarity,” Hazel said. She said the report cards are designed to give more information to parents across content areas and create more consistency from teacher-to-teacher and school-to-school about how students are graded.

But critics say that P’s are ubiquitous and that the report card falls short in highlighting strengths, weaknesses and progress. Critics also say that some students lose motivation to excel, because P’s are overly broad, sometimes given for work that could represent a 75 percent, 85 percent or 95 percent performance.

“I don’t know anyone in my community who understands what it means to get a P,” said Max’s mother, Alicia Alexion. “We roll our eyes. We say, ‘He got a P. What is that?’ ”

Michelle Gluck, vice president for educational issues for the countywide council of PTAs, said she has heard many such concerns. In April 2013, the council of PTAs passed a resolution asking for changes in the report card, including the addition of individualized teacher comments.

“Parents feel in the dark, and they don’t like that because they can’t be as involved in their children’s education as they used to be or want to be,” Gluck said.

Hazel said she has fielded few complaints from parents. She said adding teacher comments is under consideration.

“I think there are still a lot of questions, so we will need to work toward answering the questions,” she said, adding that grades of P are meaningful. “To get a P, they have a very strong grasp of the standards and indicators, so parents shouldn’t be frustrated by that.”

As the report card was first rolled out for third graders in the 2012-2013 school year, parents voiced frustration that few children seem able to attain the top grade: an ES. One father joked last year that ES stood for “Elusive Secret.” Alexion says she has heard ESs compared to unicorns: “You’ve heard of them, but you’ve never seen one.”

Responding to concerns about ES grades, Montgomery schools officials posted a guidance document describing how student lessons should include opportunities to earn top grades by demonstrating exceptional understanding.

Teachers are more comfortable than they once were with the report card, but many still see it as a work in progress, said Doug Prouty, president of the Montgomery County Education Association, the teachers’ union. “Folks have gotten used to it over time, but there are still questions about it,” he said.

One Montgomery teacher, who asked not to be named to speak freely, said the grading system was overly ambiguous, with P’s covering too wide a range of work. The teacher said it is apparent that some students have lost interest in excelling, seeing the same grade awarded for varied levels of success, the teacher said.

Jeffrey Thames, a PTA president at two Silver Spring elementary schools and founder of the nonprofit Hope Restored, said the report card has been “extremely challenging” for families with limited English ability or little experience with school advocacy.

“The parents are finding out too late that the child is struggling, especially in the minority community and in the immigrant community, due to the unfamiliar format,” Thames said.

Hazel, of the school system’s elementary curriculum team, said the report card — and explanatory information — is translated into multiple languages. She said the district encourages parents to contact teachers if they need to know more.

As some voice concerns, the report card also has its supporters.

Shannon Phelan, a PTA leader at Diamond Elementary School in Gaithersburg, called it “a complete mind-set change.” Curriculum 2.0 is better reflected in this type of report card, she said, and “it really has way more depth and is a better way, in my opinion, of figuring out where a kid is.”

Phelan points out that reading levels are cited specifically and that a P means “you got it.” For students who get an “I” for “in-progress,” she said, it’s not a failing grade. “It’s a moving-forward thing.”

In North Chevy Chase, Nick Krauze, 8, the youngest member of the Alexion-Krauze family, wondered about his music grade. Music is his passion; he plays piano and guitar. He got a P.

His mother pointed out a chart on Nick’s report card showing an uptick in Nick’s instructional reading level for the marking period. Nearby, the boy’s marks for reading were all P’s.

Looking at her older son’s report card, she pointed out he is a particularly strong math student. All four quarters, he was given P’s.

Both boys had a sprinkling of other grades, but Alexion said her sons’ experiences reflect what she sees as the problem: “They have different strengths, different weaknesses — and the same report card.”