The largest study of students at colleges that do not require SAT or ACT scores has found that there is "virtually no difference" in the academic performance (measured in grades or graduation rates) of those who do and don't submit scores.

The study -- involving 123,000 students at 33 colleges and universities of varying types -- found that high school grades do predict student success. And this extends to those who do better or worse than expected on standardized exams. So those students with low high school grades but high test scores generally receive low college grades, while those with high grades in high school, but low test scores, generally receive high grades in college.

The study was led by William C. Hiss, who has conducted many previous studies of test-optional policies at Bates College, where he was vice president and dean of admissions. His report was released by the National Association for College Admission Counseling. (NACAC has encouraged colleges to more carefully consider whether they need to require admissions testing, but the association has not called for all colleges to go test optional.)

More colleges -- including competitive colleges -- have gone test optional in recent years. The National Center for Fair and Open Testing maintains a list of more than 800 four-year colleges that do not require the SAT or ACT, although some of those colleges are not competitive in admissions.

As the numbers on that list have grown, there has been speculation about whether colleges that are test optional are paying any price in terms of the academic performance of their students. While many individual test-optional colleges have studied the issue (answering in the negative), the new report is the largest such analysis (also answering in the negative, saying that the differences are so small as to be "trivial"). Further, the report backs the thesis of test-optional advocates that such policies may help diversify the applicant pool.

Among the findings:

The difference in grades between submitters and non-submitters is five one-hundredths of a grade-point-average point.

The difference is six-tenths of 1 percent in graduation rates.

About 30 percent of students who enroll at these colleges did not submit test scores.

Students who do not submit test scores are more likely than those who do to be the first in their families to go to college, non-white, female or Pell Grant recipients.

By income group, those with the lowest and highest incomes are more likely than others to apply without test scores.

In 2008, NACAC issued a report on admissions testing, calling for colleges to step back and see if they really needed to require it. Another recommendation of the report was to produce more independent research on admissions testing (much of which is done by admissions testing organizations), and the study released came from NACAC (with foundation support) as part a response to that latter recommendation.

The new report says that its findings suggest many more colleges can drop testing requirements without any fear of an academic impact. And the report says that doing so may be especially appropriate now, when concerns are growing about "undermatching" -- the idea that many students don't end up at the best colleges at which they could succeed.

Colleges that move beyond testing requirements can attract these students, the report says. "There are dramatic choices to be made," the report says. "The numbers are quite large of potential students with strong [high school grades] who have proved themselves to everyone except the testing agencies."

The College Board released a statement from Cyndie Schmeiser, chief of assessment, that defended the SAT. "The predictive validity of college entrance exams like the SAT is an essential part of the admissions equation for the vast majority of colleges and universities in the this country. The SAT is among the most rigorously researched and designed tests in the world and dozens of internal and external studies show that the SAT is a valid predictor of college success for all students," she said.

Schmeiser said that in "nearly all validity studies, high school G.P.A. and SAT scores in combination are shown to be the best predictors of college success. The College Board continues to advocate for a variety of factors to be considered in the admissions process and high-quality research including our own shows that neither the SAT nor high school G.P.A. should be used alone when making admissions decisions."

However, she added: "It’s important to note that test-optional schools are our members and our partners. We respect the decisions they make about their admissions processes and we will continue to listen to our members, evolve our programs and work to expand access to opportunity for all students."

But Joseph Soares, professor of sociology at Wake Forest who has written extensively (and critically) about standardized admissions tests, said via email that he saw Tuesday's report as significant.

"This is important because it is our first national assessment of how well test optional is doing, and the results are solid," he said. "As we have experienced here at Wake Forest, which was one of the participants in the study, being test-optional expands opportunity for low [socioeconomic status] youths and minorities of color. The study confirms that high school grades remain the best predictor of college grades; and suggests that anyone relying on test scores reduces the breadth of their applicant pool for no good reason. Test scores transmit social disparities without improving our ability to select youths who will succeed in college."

Added Soares: "This study raises again, in my opinion, the question: If you are not test optional, how can you justify requiring a metric more social Darwinist than academic in its effects?"