All of which ignores the REAL reason that scores of niggers increased, which is that the content of Caucasoid blood in niggers increased dramatically during that time.

Do the simple math, using 13 year olds as an example.  This supposed 7 point increase in scores of White 13 year olds is bogus, since most other tests showed a decline in education quality during that time.  Even ignoring the decline, the 24 point increase in the scores of Black 13 year olds is actually 17 points.

That's a bigger increase than these scores suggest, because the lowest scoring group is Black 9 year olds who scored 190 in 1973, which is about the lowest score anyone can get.  But being conservative, and using 160 as a base score, this 17 point increase represents a 25% increase in scores for Blacks.

Since it's known that niggers are now 25% Caucasoid and 75% Negroid, we can calculate the pure Negroid score from this.  [x = Negroid score, nigger score = 0.25 x Caucasoid score of 281 + 0.75 x Negroid score = 252, x = 242.3].  In order for their scores to have increased 17 points, the percentage of Caucasoid blood would have had to increase