The U.S. government reported the highest high school graduation rate in the nation's history last month. In 2012, 80 percent of all American students received diplomas — an important milestone in efforts to reduce troubling dropout rates.

Other recent news about America's high school juniors and seniors is less encouraging, however. Many community colleges, training programs and employers report that graduates lack basic skills and that they need remedial help on things they should have learned in high school.

Another recent national study concluded that teens don't read as much for fun as they once did and that reading for pleasure drops substantially in the later teens. One researcher noted a "huge'' drop in reading among teens over the past 30 years and added that there are far too many young people who don't read well enough or often enough.

Then last week, the National Assessment of Educational Progress (NAEP) reported virtually flat test scores for 12th-graders over the past five years, and even less proficiency in reading and math than there was 25 years ago. Known as the nation's report card, the NAEP data came from tests given in early 2013 to 92,000 of the nation's 3.2 million seniors. Since 1969, NAEP has measured what American students learn in various subject areas and compared their results among states and demographic groups.

U.S. schools may be handing out more diplomas, but what do those diplomas stand for if graduates are not well prepared for work and higher education?

Experts disagree about the root causes of the stagnating scores. Some say that changing student demographics — more poor, disadvantaged students of color, immigrants, second language and special education learners — are a factor. Others argue that curricula have been dumbed down and that not enough is expected of high school students. And some note that older teens often are in "senior slump'' mode and don't take the NAEP tests seriously because they don't count toward graduation. The one point of agreement is that the nation's high school seniors need to do better.

"Stagnation is unacceptable," David P. Driscoll, the chairman of the National Assessment Governing Board, said in a statement. "Achievement at this very critical point in a student's life must be improved to ensure success after high school."

The encouraging news from NAEP is that the most recent reading and math assessments for the nation's fourth- and eighth-graders have shown significant improvement overall. Last fall, Minnesota fourth-graders scored the best in the country in math, while the state's eighth-graders ranked fifth.

Minnesota students overall tend to score in the top five among the states on national assessments, though we continue to have substantial differences among students of different races and incomes. But even on the disparities, last year's state results indicated some narrowing of the gaps in earlier grades. The key now will be sustaining that momentum as students progress.

The National Center for Education Statistics, which administers the NAEP test, did not have funding to include Minnesota among the 13 states whose results were released. The test was given to a representative sample of the nation's high school seniors between January and March 2013. Of those states whose results were released, Connecticut, Arkansas, Idaho and West Virginia made "statistically significant" gains in math scores, while only Connecticut and Arkansas gained ground in reading.

The primary message from the rash of recent reports is that more needs to be done in Minnesota and nationally to ensure that high school students are prepared for college and careers. In fact, that's crucial to success in an increasingly global economy.