College enrollment has remained at an all-time high despite predictions five years ago that it would decline as the population of 18- to 24-year-olds declined, the Education Department reported yesterday.

The department's center for education statistics projected in 1982 that college enrollment would decline from 12.4 million to about 12.1 million in 1987. But a survey conducted in the fall among more than 600 colleges and universities estimates that current enrollment is 12.5 million.

The stable enrollment was attributed to increased numbers of older and part-time students, women, foreign students and some minority groups.

"It seemed very reasonable about 1980 or 1982 to think college enrollment would be going down for a good part of the decade and into the next decade," said Vance Grant, specialist in education statistics at the Education Department. "But you've got more part-time students, more older students, a larger proportion of young women and older women. This has had quite an impact on college enrollment."

He said the numbers of Asian and Hispanic students also have increased.

The number of 18- to 24-year-olds declined from a peak of 28.9 million in 1981 to 26.5 million in 1986, a drop of 8.5 percent, according to Census Bureau statistics.

Acting on projections that student populations were bound to decline, colleges actively recruited and marketed courses to attract nontraditional students, the report said.

The survey showed that women students outnumbered men, constituting 53 percent of enrollment, compared with 49 percent in 1977 and just over 40 percent two decades ago. Part-time students accounted for 42 percent of enrollment, according to the latest statistics. That compares with about 40 percent a decade ago.

The survey also reported that the number of degrees conferred remained stable compared to the previous year, with the exception of associate degrees, which dropped 4 percent from 1986 to 1987. Women account for 52 percent of those receiving bachelor's degrees.

Reporting on the finances of colleges and universities, the department said that revenues increased 5 percent and expenditures increased 6 percent in fiscal 1987 over the previous year. The increases were higher among private four-year institutions, the report said, and lower among public two-year institutions.