A 30-point boost in math and critical-reading scores on the SAT reasoning test is statistically meaningless yet could make or break a student's chances of admission at "a substantial minority" of colleges, a research paper says.

And the more selective the college, the more that bump pays off, it finds.

The study, based on a survey of 246 college admission officials nationwide and released Wednesday by the nonprofit National Association for College Admission Counseling, was commissioned to explore the effect of test preparation for college admission exams.

But the report also raised concerns about whether some colleges use test scores inappropriately.

Independent studies estimate that coaching can improve a test-taker's math and reading scores by 30 points on average — a bump so small on the 1600-point SAT sections that the College Board, which owns the test, says it could be attributed to measurement error.

Yet in the new study, 20 percent to 40 percent of officials at 130 colleges that consider the SAT in admissions said a 20-point math increase or a 10-point reading increase would "significantly improve a student's chances of admissions" if all other factors in a student's application were the same.

"If marginal college admission decisions are made on the basis of very small differences in test scores, a small coaching effect might be practically significant," says author Derek Briggs of the University of Colorado-Boulder.

Briggs says he was "pretty stunned" by the findings, given that the College Board and makers of the ACT entrance exam caution against using scores as a sole criterion for high-stakes decisions such as admissions and scholarships. He didn't probe as deeply into ACT data, but says "it is very likely" findings would be similar.

The association said in a statement that the misuse Briggs found is a problem in "a small number of cases," but "these realities are likely to complicate the decisions of students and families trying to determine how best to allocate (time and money) related to test preparation."

Association CEO Joyce Smith says the group is planning "a new round of communications and training" for its member schools.