WASHINGTON - The Clinton administration yesterday reported modest gains in student performance on reading tests, but said they were significant because the increase reversed a downturn that occurred in the early 1990s.

“The gains are not huge, but they are statistically significant,” said Vice President Al Gore. He went to the Education Department to announce results of the survey, the National Assessment of Educational Progress, a widely used yardstick of academic performance.

The government reported test results for 31,000 children in the fourth, eighth and 12th grades. At all grade levels, scores were higher in 1998 than in 1994.

Many children were just making up ground lost early in the decade, when reading scores declined for reasons that were not clear. The performance of fourth-graders and 12th-graders was about the same in 1998 as in 1992.

Only eighth-graders scored higher in 1998 than in 1992. Despite the latest gains, most students were still reading below the levels recommended by the governing board of the testing program.

The event yesterday, with Gore in attendance, was more political than usual. Dozens of education lobbyists attended the event, in an auditorium at the Education Department. The difference in tone was noted by the collectors of education statistics, who pride themselves on being nonpolitical. The governing board defines three levels of reading achievement: basic, proficient and advanced. Only one-third of fourth-graders and eighth-graders were deemed to be at least proficient, meaning that they could understand a text and draw inferences from it.

Forty-one percent of 12th graders were at or above the “proficient” level of achievement.

Education experts note that some of the poorest students have dropped out of school by the 12th grade, and dropouts are not tested.

Tests are graded on a scale from 0 to 500. The average score for all eighth-graders was 260 in 1994, the same as in 1992, but it rose to 264 in 1998.

For black eighth-graders, the average scores were 238 in 1992, 237 in 1994 and 243 in 1998. For Hispanic eighth-graders, the scores were 241, 240 and 244, respectively.

The average score for fourth-graders of all races rose 3 points in the last four years, to 217, with most of the improvement occurring among poor readers.

The average score for 12th-graders rose 4 points, to 291, with most of the gains observed among students in the middle and at the top of the class.

Among 12th-graders, the government said, there was “no apparent difference between 1998 and 1992 in overall average scores for the nation.”

Girls scored better than boys at all grade levels. Scores for public school students were, on average, lower than the scores for children in the same grades at private schools.

Average reading scores for eighth-graders and 12th-graders at public schools did show an increase from 1994 to 1998.

The survey, known as the nation’s report card, found a widening gap between good readers and poor readers at the 12th-grade level.

From 1992 to 1998, scores declined for the lowest 10th of the senior class, but rose for the top-performing 10th of the class.

State-by-state results will be released next month.