More Americans have high school diplomas and college degrees than ever before, reflecting a continuing emphasis on education in society, a new Census Bureau study shows.

"The entire post-Second World War era has been characterized by an expansion of educational opportunities and structures in the country," Census demographer Robert Kominski commented.His new study of educational attainment found that, as of March 1987, more than three-quarters of people aged 25 and over have completed high school and nearly one in five has finished four years of college.

"In the 1960s the civil rights movement added another level of opportunity. And the expansion of college grant and aid programs in the '60s and '70s allowed this to continue," he said.

Kominski added that changes in the ages of the population have also had an impact on education averages, as the less-educated elderly are replaced by younger people who spent more time in school.

For example, people in their teens, with 80 percent to 90 percent completing high school, are replacing older folks who were raised at a time when completion of six to eight years of schooling was a major accomplishment, he explained.

Does this mean that Americans today are smarter than in the past?

"Not necessarily," Kominski said. "We all like to think that we were raised in the generation which produced the best and the brightest."