Sex and religion promise to be the main themes at tonight's Fairfax County school board meeting, as the sex education controversy reemerges and two Jewish students return to ask the board to change the graduation date at Woodson High School.

The board meeting will begin at 7:30 p.m. at the board room on Page Avenue.

The speakers' list for the public participation section of the meeting already has 11 people -- one more than usually allowed. All the speakers have signed up to present their views on possible changes in the schools' sex education program.

Members of at least two conservative groups -- the John Birch Society and Virginia Right to Life -- have signed up to speak.

The board began considering whether to revise the sex education program several months ago after the school board received the results of survey of parents in the county. According to the survey, most parents prefer a more liberal curriculum than the current program.

The school board delayed action on the issue by referring the matter to its instruction committee, which is to report back to the board tonight. While committee members say some changes may be needed in the program, they say there is little chance of making the changes by the start of the next school year.

Ann Kahn, head of the instruction committee, said the committee will recommend that school staff study alternatives to the current program and present a proposal to the school in time for the 1981-82 school year.

Another issue before the board tonight will be a petition from two seniors at W. T. Woodson High School. The students, twin sisters Lynn and Susan Stein, will ask the board to reschedule this year's graduation at Woodson High School, which now is set for a Saturday. The Steins, Jewish honor students who are among the senior class valedictorians, say they would not be able to attend since Saturday is the Jewish Sabbath.

Last month, a Fairfax judge denied the students' request that he order the change and the Steins' have filed an appeal to the State Supreme Court.