…The number of test prep centers in the U.S. more than doubled to 11,000 from 1998 to 2012, the last year for which Census data are available.
There’s a multibillion-dollar market for tutoring services in the U.S., with franchises such as Kumon and big chains including Kaplan and Princeton Review. The test prep industry promises to help students score better on everything from the SAT to Advanced Placement courses to med school entrance exams.
Strictly speaking, Kumon and similar centers do not focus on test preparation.
Washington DC, New Jersey, Hawaii, New York, and California lead in locations with the highest concentrations of tutoring establishments, as shown by the chart on the right.
All the money and effort devoted to commercial test preparation seems to have a relatively low payout.
… Contrary to the claims made by many test preparation providers of large increases of 100 points or more on the SAT, research suggests that average gains are more in the neighborhood of 30 points….