I only skimmed it (read the abstract, checked the graphs, reviewed what stuck out as I scrolled), but quick take aways:
(1) The # of private tutoring centers has tripled to 10k since 1997!
(2) The utilization of the _new_ tutoring centers is primarily by the wealthy (which obviously skews white). In fact, utilization of private tutors by low income folks has gone down in the same period.
(3) They have a section summarizing how Asian-American utilization of tutoring center is high. They even summarize/mention other work that implies tutor usage as primary factor for the high test scores of Asian American students.
I'm not sure how comfortable I am with the second-half of that last point, but finding information from a credible source (Harvard/BU/Brown) wasn't hard.
Is there reasonable evidence to show that whites and asians receive "external support" at a rate high enough to convincingly explain a 50 to 100 point disparity on this test?