Fairfax County school officials will begin this month to monitor grades of students who participate in extracurricular activities and will encourage -- but not require -- those with failing marks to get help, Superintendent Robert R. Spillane said yesterday.

The action by the area's largest school system puts it at odds with a national trend toward requiring students to attain a minimum academic average if they wish to play sports or join clubs. Locally, Prince William and Prince George's counties have imposed minimums, and the D.C. Board of Education tentatively agreed to one last month.

In Fairfax County, extracurricular coaches and sponsors will monitor students' grades starting with the third grading period, which begins Jan. 29, and check again at the end of each quarterly and interim grading period. Students participating in sports, the newspaper, yearbook, debate team and other major activities with paid sponsors will be monitored, as will all student officers.

Students who are doing poorly -- defined by grades of D or F, a drop of two letter grades or an overall decline in quarterly academic performance -- will be encouraged to seek academic help, officials said.

"It is important that involvement in extracurricular programs be kept in proper perspective and that academic progress remain the primary concern of our students and staff," Spillane said in a statement accompanying the announcement.

The Fairfax County action is similar to a program already in effect at Fairfax High School. The county School Board has discussed imposing an academic minimum several times, but has decided not to, partly because of opponents' arguments that it would be unfair to students of low academic ability whose main source of pride is in after-school activity.