The U.S. Hispanic population is burgeoning but the percentage of Hispanic youths who finish high school is decreasing, the American Council on Education said yesterday.

"The long-term costs of a failure to adequately educate large numbers of Hispanics in this country is enormous," the council said in its ninth annual report on the status of minorities in education.

The report also found that the number of blacks graduating from high school in recent years has not improved significantly.

However, the number of college degrees awarded to minority students between 1987 and 1989 increased, according to the report, which said that was a reflection of the increase in overall minority population.

Highlights of the report:

High school completion rates for Hispanics ages 18 to 24 dropped from 62.8 percent in 1985 to 56 percent in 1989. In 1989, 76.1 percent of blacks completed high school, compared with 75.6 percent in 1985 and 76.5 percent in 1986.

Asian Americans had the largest proportional college enrollment gains between 1986 and 1988 -- 10.9 percent -- while American Indians and Alaskan natives experienced the smallest increase, 3.3 percent.

In 1989, 28.7 percent of recent Hispanic high school graduates were going to college, compared to 30.8 percent of black graduates and 38.8 percent of white graduates.

Hispanics, despite their rapid growth in the U.S. population, "are grossly under-represented at every rung of the educational ladder," the report said. Only 24.5 percent of Hispanics ages 3 and 4 are enrolled in preschool programs, the report said. And just 78.7 percent of 16- and 17-year-olds are in school, compared with 91.6 percent of the total population, it said.

In 1989, there were more than 20 million Hispanics in the United States, 8.2 percent of the total population. Between 1980 and 1989, the Hispanic population grew by 39 percent, while the total U.S. population increased by 9.4 percent.

"Without immediate intervention to educate and train not only those in school now, but those who already have left school, {Hispanics} may face serious obstacles to full participation in the national economy," the report said.

The number of blacks enrolled in college reached an all-time high in 1988, but the group's rate of participation increased only slightly between 1985 and 1989.