The surge of computers into American classrooms has become a "flashy symbol of school success" that does little to improve education and may divert resources from the major restructuring needed to upgrade the nation's high schools, the Carnegie Foundation for the Advancement of Teaching said yesterday.

"The strategy seems to be 'buy computers now, plan later,' " said former U.S. education commissioner Ernest L. Boyer, the foundation's president and author of a 363-page study released yesterday: "High School: A Report on Secondary Education in America."

"All too much of today's computer instructional material resembles a book cover without pages," he said. "The technology is available . . . but educational content that makes the investment worthwhile is largely lacking."

After almost three years of study, Boyer said that American high schools, despite some successes, are generally "adrift."

Their prime needs, he said, are for a new "core curriculum," more writing by students, and better working conditions and more autonomy for teachers.

The report also calls for sweeping changes in how teachers are trained. Boyer said education as a separate college major should be abolished and education courses should be limited to a fifth year of college study that would include practice in teaching. All new teachers, he said, should be required to pass written examinations in English proficiency and the subjects they intend to teach.

The Carnegie study is the latest in a series of reports critical of American schools. The one most widely publicized, that of the National Commission on Excellence in Education, spoke in dire terms of "a rising tide of mediocrity" that threatened "our very future as a nation."

Boyer, who was education commissioner under President Carter just before the Department of Education was created, said the report card on the schools is "mixed" and "beginning to improve." Most high schools, he said, are "surviving but not thriving and . . . have little intellectual challenge." But about 10 to 15 percent of U.S. students, he said, receive "perhaps the finest education in the world."

After "a toboggan slide of decline" that began in the mid-1960s, Boyer told a news conference, "there is now a rising tide toward school improvement" at state and local levels. Efforts to impose higher standards have been under way for several years, he said, with some evidence of gains in achievement although so far these are "only marginal."

While several recent reports called for computer instruction for all students, Boyer said the schools should require a course about technology and its impact, not in how to handle computers themselves. In a few years, he said, the computers are likely to become so easy to operate that little technical skill will be needed to use them.

Although computers may be helpful for routine drill and remedial work and eventually may enrich education, Boyer said most schools are buying them "with little thought as to how they will be used and what larger educational purposes will be served." Buying them before a "core educational program is solidly in place is to turn school priorities upside down," he said.

The report includes a major compilation of other education studies and data. It also is based on month-long visits by a cadre of observers to 15 high schools in different types of communities across the country.

Boyer said one of the chief problems they found was a sense of powerlessness among teachers. In classrooms, he said, "a welter of routine procedures and outside interruptions"--from lengthy checklists of "learning objectives" to intrusive public address systems--often "dominate life . . . and, in the end, restrict learning."

Many teachers are "beaten down," he continued, and have entered into an "unwritten, unspoken, corrupting contract with students that promises a light workload in exchange for cooperation in the classroom."

Boyer proposes a 25-percent increase in average teacher pay over three years. He also presents a merit pay plan, providing ranks for teachers, that is similar to ideas backed by President Reagan.

However, he said that improved working conditions for teachers, including smaller classes, more preparation time and more discretion in choosing textbooks and developing lesson plans, "are at the center of improved teaching."

Boyer said that about two-thirds of required courses should follow a "core curriculum" that all students would study instead of moving into college prep, general and vocational tracks.

In a pattern borrowed from recommendations Boyer made several years ago for colleges, the first two years of high school would be dominated by these required courses. Electives and specialized studies, including vocational courses, would be permitted during the final two years.

Some of the report's other recommendations include:

* Emphasis on writing and the mastery of English as "the first and most essential goal of education." Boyer said writing is the "central skill that leads to clear thinking," but it is neglected by teachers who too often use multiple-choice and fill-in-the-blanks tests.

* Requirements that all students complete a written independent-study project and perform at least 120 hours of volunteer service before they can be graduated from high school.

* Replacement of the Scholastic Aptitude Test with a Student Achievement and Advisement Test that would be tied to the core curriculum. Boyer proposed that the curriculum include courses in writing, speech, literature, science, mathematics, a foreign language, western civilization and non-western studies, U.S. history, the arts, technology and health.

* A federal loan fund for repairing schools and equipping science labs.