In 1993, The New York Times reported:

On the verbal test, the average scores of black students rose to 353 this year, up 1 point from last year and 21 points from 1976. In comparison, the average score of white students was 444 this year, up 2 from last year and down 7 points from 1976.

I estimate that if all American 17-year-olds (not just the college-bound elite) had taken the SAT in the mid 1970s and mid 1990s, the verbal SAT would have had a mean of 368 (SD = 119) and 376 (SD = 119) respectively.

From here we can deduce that the mean verbal IQ (U.S. norms) of college bound blacks (as measured by the SAT) increased from 95 in the mid 1970s to 97 in the mid 1990s.  By contrast, the mean verbal IQ of college bound whites dropped from 110 to 109 over the same period.

On the math test, the average score of black students rose to 388 this year, up 3 points from last year and up 34 points from 1976. In comparison, the average score of white students was 494, up 3 points from last year and up 1 point from 1976.

I estimate that if all American 17-year-olds (not just the college-bound elite) had taken the SAT in the mid 1970s and mid 1990s, the math SAT would have had a mean of 402 (SD = 124) and 411 (SD = 133) respectively.

From here we can deduce that the mean math IQ (U.S. norms) of college bound blacks (as measured by the SAT) increased from 94 in the mid 1970s to 97 in the mid 1990s.  By contrast, the mean math IQ of college bound whites dropped from 111 to 109 over the same period.

From the article it can be deduced that the combined score (verbal + math) of college bound blacks increased from 686 in the mid 1970s to 741 in the mid 1990s.  By contrast, the combined score for college bound whites dropped from 941 in the mid 1970s to 938 in the mid 1990s.

I estimate that if all American 17-year-olds (not just the college-bound elite) had taken the SAT in the mid 1970s and mid 1990s, the combined SAT would have had a mean of 770 (SD = 200) and 787 (SD = 208) respectively.

From here we can deduce that the mean full-scale IQ (U.S. norms) of college bound blacks (as measured by the SAT) increased from 94 in the mid 1970s to 97 in the mid 1990s.  By contrast, the mean math IQ of college bound whites dropped from 113 to 111 over the same period.

So the bottom line is that among college-bound 17-year-olds, the black-white IQ gap (as measured by the SAT) shrunk from 19 points to 14 points as measured by U.S. norms, or 20 points to 14 points as measured by U.S. white norms.

This is the same story as told by the NAEP, which showed an even more dramatic reduction of the black-white IQ gap in the general U.S. population (not the college bound elite).  However no such reduction was observed on the Wechsler intelligence scales where the black-white gap has remained 15 points from the 1970s to the 2000s.

Tentative conclusion: scholastic tests gave biased measures of black IQ at least until the mid 1970s, but by the mid 1990s, they gave results commensurate with official IQ tests like the Wechsler.  Black Americans who use the scholastic tests to estimate their IQs should add 5-10 points if said tests were taken before 1975 or so.