Concerned that student writing suffers from neglect outside Expository Writing classes, Expos Director Richard C. Marius is offering professors and teaching fellows a lesson in grading.

The average instructor's grading rates about a C-plus or a B-minus, Marius said yesterday, citing a need for stricter standards and more explicit commentary.

In an effort to help graders make the grade, Marius sent each department copies of his own 10-page "Guide To Grading Papers at Harvard" earlier this year and offered to run private seminars on the subject.

Marking papers "is one of the most significant parts of a student's education. If we take teaching seriously, we must take marking papers seriously," Marius wrote in his grader's manual.

"Usually, the reasons for the grades are not spelled out for students, and the grading of papers is almost always too high," he elaborated yesterday.

To date, only the Dunster House tutors and the Sociology Department have taken him up on his seminar offer, but Marius said he remains hopeful that interest will eventually increase.

The current initiative is the latest chapter in Marius's ongoing campaign to make writing a higher priority at Harvard. It was intended to prevent undergraduates' prose from deteriorating after Expos, Marius's associates said.

"Very often, students lose the skills they acquire in Expos before they graduate because there is not enough reenforcement of those skills," said Professor of Romance Languages and Literatures Donald A. Stone, a member of the faculty standing committee on Expos.

Marius said graders do students a disservice by focusing on the content of their papers and ignoring the quality of the writing.

The "Guide to Grading" instructs teachers to evaluate undergraduate writing with four factors in mind: the clarity of the message, the logic, the style, and the value of the author's effort.