Among the things that Harvard has found out about you but will never, never tell is a little number known as your predicted rank list, or PRL.

PRL is a statistical guess of how each student will perform academically at Harvard. It is accessible only to admissions officials and to advisors. Both have been sternly admonished by the college not to divulge the secret numbers to any students.

Why should the students want to know? Well, PRL is the closest thing Harvard has to a how-smart-are-you index, and because of that is one of the College's greatest status symbols. Does ranking first in your class at Exeter make you smarter than a science type who gets a bunch of 800 board scores? It's hard to say. PRL is Harvard's answer to such questions; it is a tidy composite of your high school academic achievements and what the College knows of your aptitude.

No Bragging

One reason for Harvard's shrouding of the numbers in secrecy has been the desire to prevent the higher rated students from blabbering. "My PRL is better than your PRL." and the like. "It would be unhealthy to brand people." one senior tutor explained.

Despite the lid of censorship, there are those lucky students whose freshman advisors have let the magic number slip out in the course of cocktail conversation, and those doubly lucky ones, who, when told their number, found it was a good one. A smiling senior in the second category confided, "I've been group five for three years running, but I'm always able to say. "I'm smart; the College had me pegged for group two."

Unfortunately, only a few of us have had such loose-lipped advisors. But college officials have revealed enough about PRL to enable the student to make an educated guess at his own number.

Contrary to most student belief, there are only three factors in the PRL formula-rank in class, the College Board verbal aptitude test score, and an average of College Board achievement test scores. (One misinformed student swore to the interviewer that there were "about 26" factors in the formula and that one of them was whether the student's parents have been divorced.)

PRL is computed for all applicants to the college and ranges from 1.4 to about 7. "The lowest I've ever seen is 7.1," Fred L. Glimp, Dean of College and former Dean of Admissions, said, "And that's a heck of a low PRL." Ratings from 1.5 to 2.4 are a prediction for group two performance: from 2.5 to 3.4 for group three, and so on.

According to Dean K. Whitla. Director of the Office of Tests, to get a 1.4 rating, a student must "rank first in a class of about 1000 and have all 800 board scores. So, it's obvious that we seldom predict a boy for group one."

Cut-Off

Whitla said that a PRL of 6.0-a prediction of unsatisfactory performance-is generally the cut-off point for applicants, although exceptions are sometimes made, particularly in the case of foreign-born students or students coming from a disadvantaged background.

Students ranking below 6.0 are usually admitted only if they appear to be the "happy bottom quarter type." according to Glimp. "That's the kind of guy whose temperament is such that he won't mind holding up the rest of the class."

The PRL formula is empirically derived from the actual rank list standing of Harvard students and is revised whenever a significant error shows up-about once every three years.

The information from actual standings is translated by computers into curves representing the relative advantage for performance at Harvard of the whole range of verbal aptitude and achievement scores. Several curves of like derivation are drawn for rank in class to take care of the wide variance in the size of high school classes.

The actual scores and class ranking are the variables in these three formulae. To find the PRL, the derivatives from the three are weighted in one of two proportions, depending on whether the applicant comes from a public or private school. In the public school formula, the class ranking derivative is 47 per cent of the PRL, verbal aptitude 23 per cent, and the average of achievement scores 30 per cent. For private school graduates it is 48 per cent, 20 per cent, and 32 per cent.

Aptitude is more heavily weighted in public schools because the quality of instruction is slightly lower. But according to Whitla, with each revision of the PRL formula the percentages come closer to identity, "probably because the teaching in public schools is improving."