The nation’s schoolchildren have made little or no progress in reading proficiency in recent years, according to results released Wednesday from the largest nationwide reading test. The scores continue a 17-year trend of sluggish achievement in reading that contrasts with substantial gains in mathematics during roughly the same period.

“The nation has done a really good job improving math skills,” said Mark Schneider, a vice president at the American Institutes for Research and a former official at the Education Department, which oversees the test, known as the National Assessment of Educational Progress. “In contrast, we have made only marginal improvements in reading.”

Why math scores have improved so much faster than reading scores is much debated; the federal officials who produce the test say it is intended to identify changes in student achievement over time, not to identify causes.

In seeking to explain the lagging reading scores, some experts point to declines in the amount of reading children do for pleasure as they devote more free time to surfing the Internet, texting on cellphones or watching television. Others blame undemanding curriculums.