CHICAGO -- A debate among American educators over how to improve the education of low-income blacks and Latinos has erupted again with the release last week of an extensive University of Chicago study showing a 10-year decline in achievement in minority schools.

The study by the Metropolitan Opportunity Project here focuses on 438 high schools in four southern California counties, documenting a trend researchers here say they have also seen in Chicago and Atlanta.

The report says that schools with high concentrations of poor minority children showed lower average scores on standarized tests in 1985-86 than on the same tests 10 years before.

Gary Orfield, political science professor and project director, said recent school policy changes forcing higher standards on such students "will be counterproductive" unless accompanied by renewed efforts to move poor minority students into middle-income area schools and greatly increase spending in low-income area schools.

"The belief that more can be demanded while less assistance is provided is rooted in a radical rejection of the understanding of the 1960s," Orfield said in an introduction to the report by project staff member Christopher Jaeger.

Orfield said the study supports the notion, popular in the 1960s, that special programs are needed and undercuts the 1980s assumption "that equal opportunity already exists and that the reason . . . inner-city schools are failing is that they and their students have not been subjected to increasingly coercive and demanding requirements."

California education officials, who have chosen to try to raise standards in inner-city schools without significant new efforts at mixing lower- and upper-income students, challenged the study's conclusions and said it overlooked a significant rise in low-income minority test scores in the last four years.

"This kind of study feeds the doubts of some people, just when we're getting the situation somewhat turned around," said Bill Honig, state superintendent of public instruction. "We're showing that these kids can learn, but this just makes it harder."

Honig and many other supporters of recent educational reforms support Orfield's call for more money and resources in low-achieving schools but insist that standards also must be raised or teachers and students will not be motivated to take advantage of the new opportunities.

The Los Angeles Unified School District, with the highest concentration of poor minorities, showed the sharpest decline in the Chicago study of scores on the California Assessment Program test of basic academic skills. On the average, Los Angeles high school seniors dropped 4 points in reading, 2.6 points in mathematics and 1.8 points in writing from 1976 to 1986.

The Chicago study showed that the gap in average scores between the top 10 schools there, usually predominantly Anglo or with special admissions standards, and the bottom 10 schools, overwhelmingly black or Latino, widened by 5 or 6 percentage points during the same period.

While acknowledging the 10-year decline, California state officials pointed to an upturn since 1983, when the state increased education spending, raised graduation standards and lengthened the school day. They said the mean reading scores at predominantly minority schools increased from 54.6 in 1983-84 to 56.5 in 1986-87. Mean mathematics scores increased from 58.7 to 61.2 in the same period.

In some schools where administrators and teachers have been particularly energetic in raising standards, the increase has been greater. Garfield High School, an East Los Angeles school with a 97 percent Latino enrollment and more than 80 percent of students on the federal subsidied lunch plan, raised its reading score from 51.8 to 55.2 and its mathematics score from 57.6 to 63.7. The Chicago study cited Garfield, and a few other minority schools, as exceptions to the general 10-year decline in scores.