The D.C. Board of Education tentatively voted Wednesday night to adopt a new policy requiring that all students maintain at least a C average to participate in extracurricular activities, including athletics.

The board told school administrators to begin writing the new policy that will come back to the board for a final vote in March. Board members said they want the policy to take effect in September.

"We need to alert the students now," said school board member Eugene Kinlow, whose Committee on Student Services recommended adopting the C average policy now in effect in Prince George's County. "We don't want any students in September telling us they didn't know what was going on."

If the rule is adopted in March, students who wish to participate in extracurricular activities in the fall would have to have a C average when school ends this June.

The board voted to exclude a recommendation that would have allowed students with less than a C average to take part in extracurricular activities if they joined a grade-monitoring and tutoring system.

"Are we serious about the C average or are we not serious?" said board member David H. Eaton, who said that he did not want to create any "loopholes."

In a report released last month, a survey of the grades of 303 students in four city high schools found that most students involved in extracurricular activities already had averages of C or better and would not be affected by the rule.

But students involved only in athletics generally had lower grades than students involved in either nonathletic activities or a combination of sports-related and nonathletic programs, the report said.