State test scores for elementary and middle schools in Montgomery and Prince George’s counties continued to inch — or, in some cases, centimeter — upward this year as most schools in Maryland reached new academic targets.

A Washington Post analysis of test data that state officials released Tuesday shows that nearly 91 percent of Montgomery elementary students passed the 2012 Maryland School Assessments in reading and math. That was up about two percentage points from 2008, and four-tenths of a percentage point higher than last year.

In middle schools, the passing rate for the county was about 85 percent, up about three points over four years, and three-tenths of a percent from last year.

“Five or six years ago, we saw big jumps,” said Montgomery schools spokesman Dana Tofig. But after proficiency rates climbed past 80 percent, progress started to level off. “Obviously, you want to continue to see everything point up,” he said, but it’s gotten harder.

In Prince George’s, there have been bigger gains in the passing rate — from 75 percent in 2008 to 81 percent this year in elementary grades, and from 60 percent to 68 percent in middle schools. But the growth since last year was, like Montgomery’s, small. At the elementary level, the gain was less than half a percentage point.

The Post’s analysis combined passing rates for reading and math. It showed the statewide average passing rate was 88 percent at the elementary level (grades 3, 4 and 5) and 79 percent at the middle level (grades 6, 7 and 8).

Schools remain under pressure to show improvement, even as they are preparing for new standardized tests aligned to national standards expected to roll out in the 2013-2014 school year. Seven thousand teachers across the state are undergoing training this summer on the standards. Montgomery elementary teachers are already teaching a new curriculum to students in the early grades.

States report scores annually under the 2002 No Child Left Behind law, which set a controversial target that all children should pass grade-level tests by 2014. But that ambitious benchmark put an increasing number of schools on a path to failure. By last year, 44 percent of all elementary and middle schools across the state fell short of the testing goals.

This year, Maryland and 25 other states, including Virginia, received a federal waiver from the 2014 expectation.

Under the waiver, annual test scores will continue to be reported. But the way schools are evaluated has changed. There won’t be labels of “adequate yearly progress,” or of failing to meet AYP.

Maryland’s new system expects continuous improvement, but not perfection. Each school must be on track to cut its portion of non-proficient students in half by 2017 — overall and among groups of students, based on race, ethnicity, poverty and disability status. Schools designated as failing no longer are required to offer extra tutoring services or transfers for students to other schools.

Statewide, 85 percent of schools met targets called “annual measurable objectives.” Prince George’s officials said 63 percent of their elementary and middle schools met the AMO targets. Montgomery officials released no comparable rate Tuesday.

As overall improvements have slowed, school systems continue to scrub the data to monitor progress for individual schools and to chart efforts to close achievement gaps based on race or class.

In Prince George’s, Doswell E. Brooks Elementary School in Capitol Heights made the highest annual gains in reading, with 92 percent of students rated proficient this year, up from 75 percent in 2011.

Three of the county’s middle schools made double-digit gains in math passing rates this year: Hyattsville, Kenmoor and Benjamin Stoddert.

In Montgomery, elementary reading performance held steady for most racial and ethnic groups, but dropped slightly for African American and Hispanic students in middle grades. In math, the proficiency rate for African American students grew nearly two percentage points in elementary grades and three points in middle grades.

Montgomery officials also were monitoring how many students passed the tests at an advanced level.

More than half of Montgomery middle school students — 56 percent — scored advanced on state reading tests, exceeding the state average of 44 percent and Prince George’s rate of 30 percent. In math, the advanced passing rate for middle schoolers was 39 percent in Montgomery, 32 percent statewide and 17 percent in Prince George’s.

Montgomery Superintendent Joshua P. Starr argues that standardized test scores should not be relied upon too heavily for determining the success or failure of schools or teachers.

“If we are serious about wanting to improve education for all students, we must develop more accurate ways of measuring the quality of instruction and the engagement of students,” he said in a statement.

Maryland is in the process of developing a more complex way to evaluate schools, based on performance and progress. It will include test scores and metrics for how much schools are closing achievement gaps and how well they are preparing students for college and careers. The new rating system should be released by early fall.

Test results for the District and Virginia are expected this summer.