The Fairfax Education Association said yesterday it intends to file suit today in federal court in Alexandria, alleging that a Fairfax teacher's right of free speech was violated by county school officials.

The announcement by the FEA, which represents most of the county's public school teachers, came as a two-week-old pay-related protest by the teachers continued.

In a related development, about 400 students at Oakton High School walked out of their second period classes yesterday, saying they were acting in support of teacher demands for larger pay raises. The hour-long walk-out involved about 16 percent of the student body.

Oakton principal Rudolph Bush called the student protest orderly and said there were no suspensions.

The threatened lawsuit involves Charles Rayburn, 42, a math teacher at Groveton High School. FEA officials said Rayburn, former head football coach at Groveton, was relieved of his coaching duties last November after he criticized the school's athletic program in a newspaper interview.

School officials yesterday denied that Rayburn's firing as coach resulted from the interview, but declined further comment.

Rayburn, appearing at an FEA news conference, said he spoke to an Alexandria Gazette reporter last fall "because I was concerned with the program here." In the interview, Rayburn said the school was "operating sometimes with less than first-rate equipment with regards proper safety."

Rayburn said he was told by the principal, R. Don Ford, on the day after publication that he would not be returning as coach.

Rayburn said he lost a $1,480 stipend paid for his coaching duties, although he continued on the faculty as a math teacher at an annual salary of $20,000.

FEA head Bob Hicks yesterday called the Rayburn incident an "example of the kind of oppressive system we have in Virginia, where a teacher can be fired for whatever the system deems insubordination."

Hicks also called the walkout by Oakton students "tratifying."

In a related development, the FEA declared yesterday "take-down day" and asked teachers to remove materials they had either purchased or brought into their classrooms.Several school observers said the results were "spotty."