"It cannot be coached very easily."

(1) This is not a universal conclusion.

(2) Many forms of "coaching" are lumped together here. In fact some may only add 30 pts or less while others add over 100.

(3) Controlling for self-selection is self-defeating here since poor black/hispanic/native american kids don't have the same opportunity to self select into say private schools with test prep programs.

(4) Taking post PSAT gains ignores coaching received prior to this.

(5) This only measures indirect coaching. The effects of a superior school itself could be large.