Tutoring services for graduate school admissions tests have no proven value, Dean K. Whitla, director of the Office of Tests, said yesterday.

"Services of this type are generally not very functional," Whitla said. "There is no documented proof that last-ditch cram courses improve test scores."

One such tutoring firm--Kaplan Educational Center--has posted advertisements in all the Houses, offering tutoring programs designed to prepare juniors and seniors for graduate admissions tests.

Hundreds of Letters

Stanley H. Kaplan, president of the firm, said yesterday that he has received hundreds of letters from students who found his courses effective.

Kaplan, who has been offering tutoring programs since 1938, said that it is impossible to prove that his courses improve scores, because most students take admissions tests only once.

"But most of our students are referred to us by previous customers, so they must believe it is effective," he said.

Kaplan said faculty members at several Eastern colleges have recommended tutoring programs, although no Harvard professors have done so. About two hundred students in Boston enroll in his courses annually, he said, but very few of these attend Harvard.

Not Worthwhile

"I just don't think it's a worthwhile way to spend your money," Whitla said. Kaplan's courses include six sessions and cost $200.

Tests used by graduate school admissions offices--such as the Graduate Record Examination (GRE), the Law School Admissions Test (LSAT), and the Medical College Admissions Test (MCAT)--are all administered by the Educational Testing Service (ETS).

The ETS, a Princeton-based firm, also advises against tutoring programs. They say that tutoring will not affect the score any more than retaking the tests at a later date.