LOS ANGELES, JULY 1 -- For the first time in history, more than half of the nation's 2.2 million public school teachers have advanced degrees, a National Education Association survey has found.

The extensive study of the status of American teachers, the first in five years, indicates that teachers also have reached unprecedented levels of experience, salary and hours spent on the job.

But despite the signs of growing professional status for education, NEA leaders pointed to several problems: a possible decline in the percentage of black teachers, continued assignment of some teachers to subjects outside their specialties and a remarkable proportion of teachers -- nearly half -- who say they are only 15 years from retirement.

NEA President Mary Hatwood Futrell, releasing the report at a news conference during the NEA annual meeting here, applauded the progress in advanced degrees.

"This is a far cry from 1961 when less than a quarter of all teachers had earned a degree beyond the bachelor's," she said. "Back then, almost 15 percent of teachers had less than a bachelor's degree, while today, virtually all teachers -- 99.7 percent -- have at least a bachelor's degree."

The 1986 survey of 1,291 teachers, selected to represent the broad range of kindergarten to 12th-grade teachers, said 50.7 percent had master's degrees or the equivalent and 0.7 percent had doctorates. Their median total teaching experience was 15 years, up from 12 years in 1981, and the highest ever recorded by the survey, which has been done every five years since it began in 1961.

The mean salary of a teacher with a master's degree or higher was $18,788 in 1981 and $27,036 in 1986, according to the survey, a 44 percent increase.

The mean number of pupils taught per day by secondary and departmentalized elementary teachers continued its steady decline, from 132 in 1966 and 118 in 1981 to 97 last year.

Futrell noted that the average teacher last year spent 48.7 hours a week performing some teaching duty, the highest figure recorded. The survey indicated that about one-fifth of that time was spent in unpaid activities such as advising school clubs.

The survey showed that the percentage of black teachers had dropped from 7.8 percent to 6.9 percent of the total since 1981. "By 1990, if present trends continue, minorities will make up about a third of all students and only five percent of all teachers," Futrell said.

NEA survey expert Ronald Henderson said the percentage decline of black teachers was too small to be statistically significant but was still meaningful at a time when minority student enrollment is increasing.

The survey showed that the percentage of Latino, Asian and other nonblack minority teachers increased from 0.7 percent in 1981 to 3.4 percent last year, a number Futrell said was still far too low. Only when the schools succeeded in moving more minority students into academic, college-preparatory courses would the number improve, she said.

Futrell also emphasized an increase, from 16 percent to 17.1 percent, in the portion of teachers assigned to a subject outside their college specialties, after a steady drop in this category. The report said the increase was too small to "be considered indicative of a trend."

The proportion of teachers who moonlighted in nonschool jobs during the summer increased from 28 percent to 33.3 percent.