A note from home no longer carries enough authority to automatically excuse a student from class in Alexandria's secondary schools, under a revised attendance policy unanimously approved last night by the city's School Board.

For the last two years, school officials said, there has been confusion about what constituted truancy and under what conditions a student could be excused from class.

"There's not a day that goes by when I don't have students coming to me with notes from Mom asking that they be excused" for a wide variety of reasons, said Hazel Rigby, an English teacher at T.C. Williams High School and president of the Education Association of Alexandria. "The student just doesn't realize that a note from home is not going to keep them out of trouble." Some of the reasons given in the notes for absences--such as oversleeping--aren't considered good enough.

The revised policy, which applies only to the system's junior and senior high schools, defines truancy as any absence or class cut "not approved by the school."

Board members argued for more than an hour whether approval of a parent or guardian should be required. Finally, prodded by board member J. Harvey Harrison Jr., the board voted 5 to 4 to drop a requirement for parental approval of absences, although school officials can decide to take parental views into account in dealing with individual requests for absences.

Henceforth, students who accumulate more than 10 absences or class cuts will be denied class credit.

The policy provides for an appeals procedure in which a student, accompanied by a parent or guardian, can attempt to justify absences. If the school administration finds that absences were for approved reasons such as long-term illness, medical appointments or extraordinary conditions, the student will be permitted to make up the missed classwork and receive a grade.

The previous policy on absences, which did not define truancy, was criticized by parents as unclear.

Joel Freed, chairman of the ad hoc committee of parents and teachers who recommended the changes, said he thinks the revised policy will "minimize" any future controversy.