Carson City sophomores and eighth-graders scored above the state average on the TerraNova Achievement Test, while the fourth-grade students' scores were below that average.
Associate Superintendent Dorothy Todd said there are various reasons why the older students scored higher on the test.
"During those formative years of K-4, the children are learning so many different skills and they all learn at a different rate," she said. "By the time they're in middle school and high school, they can apply those skills."
She said the middle- and high-school students have also been in the district longer and have benefited from a variety of programs implemented to raise standards.
The TerraNova exam tests students nationally in reading, language, math and science. The test is taken across the nation in October.
"It's a way of telling how our students are doing in comparison with the rest of the nation," Todd said.
Carson City middle schools improved TerraNova test scores from a year ago while the high schools scored slightly lower and elementary schools dropped in reading and math but improved in language.
The percentage scored by a school is based on a national average. For example, Bordewich-Bray Elementary scored a 40 percent total score, which is better than 39 percent of fourth-graders nationwide.
Two elementary schools, Mark Twain and Seeliger, raised their total score percentiles from last year and the rest dropped.
Mark Twain went from 40 to 41 and Seeliger from 53 to 57.
Seeliger and Fritsch elementary schools received the highest scores, both having a total score of 57, which was higher than the 54 state average.
Carson Middle School dropped from last year's total score of 62 to 60, while Eagle Valley Middle School raised its total from 50 to 55. The state averaged 51.
Carson High School fell from a total of 64 last year to a total of 59 this year, although it still topped the state average of 53.
Todd said teachers districtwide are working to improve scores.
"My concern is we really need to work to raise our scores," she said. "We're certainly being as proactive as possible."