Charles Mostoller / Reuters

For generations, two numbers have signaled whether a student could hope to get into a top college: his or her standardized test score and his or her grade-point average.

In the past 15 years, though, these lodestars have come to mean less and less. The SAT has been redesigned twice in that time, making it difficult for admissions officers to assess, for instance, whether last year’s uptick in average scores was the result of better students or just a different test. What’s more, half of American teenagers now graduate high school with an A average, according to a recent study. With application numbers at record highs, highly selective colleges are forced to make impossible choices, assigning a fixed number of slots to a growing pool of students who, each year, are harder to differentiate using these two long-standing metrics.

Eighty percent of American colleges accept more than half of their applicants, but at the country’s most selective schools, there is something of a merit crisis: As test scores and GPAs hold less sway, admissions offices are searching for other, inevitably more subjective metrics.

Each year, the professional association representing college-admissions officers asks its members about the top factors they consider when making decisions about applications. Grades, test scores, and the strength of one’s high-school curriculum still remain at the top of that list. But other criteria are playing a larger role than they used to: Students’ “demonstrated interest” in enrolling at a particular school, as measured by their visits to campus or what they say in their application materials, among other things, is critical. In addition, admissions officers at about half of the institutions surveyed said an applicant’s “ability to pay” was of at least “some importance” in application decisions.

“You can’t go to a college fair anymore and say you have these grades and you’re in,” said Eric J. Furda, the dean of admissions at the University of Pennsylvania. While an applicant’s high-school GPA and test scores still carry considerable weight in admissions decisions at Penn, which had 40,000-plus applicants in the admissions cycle that ended this spring, those numbers are what Furda called a “snapshot” of a student’s life—grades from a few years of high school, or how one performed on a test on a particular day.

Furda encourages his admissions counselors to balance the “absolute merit” of grades and test scores with what he calls the “relative growth and trajectory” of applicants. “Our evaluation process looks at where they are right now and what can we expect from them once they come to our campus,” Furda said. Take, for example, applicants from private high schools or top public schools. “We expect them to have high test scores and grades,” he said. “That’s a given. So another way for us to think about merit for those applicants is, what did they do with that opportunity they were given? How far did they travel in their high school journey?”

Applicants will have a far harder time acting on such guidance than if securing admission were as clear-cut as getting a 1500 on the SAT and a 3.8 GPA. It was never quite that simple, but Furda noted that the admissions system has changed drastically in the past few decades: For the high-school graduating class of 1991, Penn accepted nearly half of its applicants. This year it accepted just 8 percent, a record low.

Applying to college has become much more stressful in the intervening years—and it only is becoming more so, as high test scores and GPAs become less certain indicators of acceptance. These days, applicants and their parents demand “absoluteness” in admissions, said Furda, who every April answers complaints from rejected applicants who compare their academic backgrounds to those of accepted students they know. The issue for Penn and other top colleges is that as applicants’ test scores and grades rise, the ability to distinguish among them becomes ever more difficult, if not impossible.

This challenge comes as Penn and other selective colleges are under pressure to increase their enrollment of low-income and first-generation students. Whatever changes they make to their admissions policies, particularly how they weigh test scores and grades, will surely be noted by competitors but also by less selective schools. “The admissions process is what it is because of the top colleges,” said Jon Boeckenstedt, the associate vice president for enrollment management and marketing at DePaul University. “They have the influence to change it.”

Indeed, when I told one admissions dean at an Ivy League school that I’d heard that another selective college might drop its standardized-testing requirement in the coming months, his reaction was one of relief. “That would give me an opening to follow,” he said. “We just can’t be first.”

Some colleges, however, are not waiting on their peers and instead are proactively coming up with different frameworks. “We’re not trying to find some formula that takes 11,000 applicants and lines them up from No. 1 to No. 11,000,” said Andrew B. Palumbo, the dean of admissions and financial aid at Worcester Polytechnic Institute in Massachusetts. “If that were the case, one of our students could create a computer program and put us out of a job. We are trying to find the best fit.”

Worcester, which this spring let in 42 percent of applicants, is one of the many colleges that no longer requires SAT or ACT scores, a decision in 2007 that was surprising given the school’s science and engineering focus. But Worcester puts its students through a project-based curriculum for four years, and to succeed in such an environment, Palumbo said, applicants must demonstrate that once on campus they can apply skills that “standardized tests don’t measure very well, if at all”—the ability to work in teams, communicate, and solve problems on the fly, for example.

More than 1,000 colleges nationwide have come to a similar conclusion about standardized tests, having dropped them as an admissions requirement. That number includes even some selective campuses such as George Washington, Wake Forest, and Wesleyan. There are good arguments supporting these schools’ decisions: for instance, that standardized test scores are highly correlated with family income.

Schools that minimize test scores, however, are often trading one inequitable measure of merit for another. Demonstrated interest has become a popular concept among admissions deans in recent years, but it too likely correlates with wealth—traveling for college visits isn’t free. And one of the best indicators of interest is applying early decision, a process that favors applicants who often don’t need to worry about comparing financial-aid offers from multiple schools.

That is to say, different does not necessarily mean better. Even if colleges are newly emphasizing certain measures of applicants’ excellence, there’s an uncomfortable underlying truth that remains unchanged: When schools with anywhere from several hundred to a couple thousand slots are picking from tens of thousands of applicants, a good amount of deciding who gets in is going to be arbitrary.