He says firms like Kaplan and Princeton Review have come along way from their humble origins. Particularly in the last decade, he says, the test prep business has boomed.

"What economists call the return to education has been increasing very dramatically," Lemann says. "Back in my era, the smart kid in California would go to Stanford or Berkeley. Now the smart kid...is much more likely to apply to Harvard. You have a bigger pool of people chasing a fixed number of slots in the top professional schools."

In addition, Johnson says, the prosperous economy has meant both that more students are interested in higher education and can afford test prep courses.

"There are more students taking courses than five years ago, two years ago," he says. "The stakes are a little higher, the competition is fiercer."

In such a rarefied admissions environment, every possible edge counts, test prep companies argue.

"The difference between getting a 163 and a 168 is the difference between going to B.C. and going to Harvard, and that is worth paying for," Freiser says.

The result is often an "arms race" mentality: as more and more applicants take commercial prep courses, the pressure on others to enroll in such courses mounts.

"Taking a commercial course may no longer be an edge, it may be a bare minimum to keep up," Freiser says.