Fairfax County School Superintendent Robert R. Spillane said yesterday he would like to raise teachers' starting pay in the county to $20,000 next year, but County Board Chairman John F. Herrity cautioned later that it may take two years to reach that level.

Beginning teachers in Fairfax earn $18,385 a year, or more than in any other area jurisdiction except Arlington, which pays $18,670, and well above the national average of $14,500. An increase to $20,000 would amount to about a 9 percent raise.

Proponents say that higher entry-level salaries are needed because the nation faces a teacher shortage that already is showing up in a lack of science and mathematics instructors. In Fairfax County, Spillane frequently reminds audiences, there were only two applicants for an opening this year as a physics teacher.

"In today's society, a starting salary of $20,000 is an absolute minimum," Spillane said yesterday. "I'm talking about next year."

Herrity, whose board of supervisors holds the purse strings for the county schools, said he supports "some sort of two-year program to increase teacher starting salaries to $20,000, or thereabouts." He said the program should take the form of two annual increases of equal size, which would be about $800 each, on top of the yearly cost-of-living raise, expected to be 3 percent or 4 percent this year.

The county government may get some of the funds for higher teacher pay from the Virginia General Assembly. Democrat Gerald L. Baliles, who was elected governor Tuesday, has pledged to make higher pay for teachers one of his administration's top priorities.

Herrity said he has told the superintendent what he supports. Spillane said he favors a larger increase in starting salaries than Herrity, but that whether he would propose a specific figure depends on how much money the supervisors give the schools.

"As long as everyone is thinking the same way, the details can be worked out," Spillane said.

Another supervisor, Thomas M. Davis III (R-Mason), agreed on the need for a $20,000 starting salary and endorsed increases for experienced teachers to keep them from leaving the school system.

Spillane said he would like a general salary increase, an increase for starting teachers, and an increase in special categories such as experienced "master teachers," who might be offered $50,000 a year. In fields where there are shortages of teachers, he said, the county may relax its rule against granting newly hired teachers more than five years' credit for previous experience.

Donna Caudill, president of the Fairfax Education Association, which represents teachers and other school employes, said she would welcome a higher starting salary for teachers, and that her association endorses higher pay at the upper ends of the experience scale.

But she said that it would be unfair to pay teachers in one field -- such as science, for example -- more than any other.