At first glance, the results of a U.S. Census Bureau study released this week look heartening. It seems that, as of last year, more Americans had high school and college diplomas than at any other time in history.

But don't start cheering yet. The results of a Department of Education study throw cold water on that achievement.According to the Education Department's "Science Report Card," in 1986, only 7 percent of American 17-year-olds had sufficient skills to do well in college science courses. And fewer than half had enough science background to perform jobs requiring technical skills.

The report paints a gloomy picture of a rising generation of scientific illiterates, a picture with disastrous implications. When an illiterate competes against an educated person, guess which one wins? The same thing goes for nations as well as for individuals. Consequently, all the trade protectionism in the world won't save the U.S. economy from foreign competition if only a small percentage of Americans can understand basic scientific concepts.

What's worse, science achievement measured for 17-year-olds in 1986 was well below the level for 17-year-olds in 1969.

It is encouraging that more and more Americans are getting high school and college diplomas. But how much are those diplomas really worth if the graduates know less than their parents did 20 years ago?

Other countries are turning out students who know a seismograph from a semiconductor. American educators have some explaining to do as to why their students are falling further and further behind.