A whole new employment world may be waiting by the time today's high school graduates begin full-time careers, according to occupation experts and forecasters.

It is predicted that today's assembly line workers will be replaced by robots, and even high-level advisers may be made obsolete by the vast amount of information becoming available via computers. Although sources disagree about specifics, most agree that the increases will largely be in the high-technology and service-related jobs, such as health care assistants and information processors, by 2000.

The U.S. Department of Labor predicts the following occupations will grow faster than average in coming years: computer programmers, computer service technicians and systems analysts; health services administrators, occupational and physical therapists; mechanical and electronic engineers; office machine repairers, electrical technicians and tool programmers; and legal assistants.

Marvin Cetron, a nationally known forecaster in Arlington, claims that the government estimates are inadequate because they are based on historical trends instead of interviews with major employers, private economists, industry associations and social service organizations. Cetron's book "Jobs of the Future," used in Fairfax County schools' career resource centers, created job titles for high-tech and specialized service delivery positions that are not included in the government listings. And Cetron challenged the education community with his proclamation that students will be ill-prepared for the emerging job market.

Among the key predictions in Cetron's study: Service sector jobs (such as telephone marketing, geriatric social workers and machine maintenance technicians) will increase from 68 percent of the workplace to 86 percent, with almost half of those jobs related to information processing.

*Writers, artists and musicians will be among the highest paid, because their talents cannot be replaced by robots or computers.

* Manufacturing jobs will fall more than 50 percent so that only 11 percent of the work force will be in smokestack industries.

* Retraining will be required every five to 10 years because of the complexity of jobs and changes in technology.