For the cross-racial validity of my method, whilst I await for contrary or supporting empirical evidence, I usually appeal to Newton's four rules of reasoning, and especially rule n.2 and 3:

2. Therefore to the same natural effects we must, as far as possible, assign the same causes.
As to respiration in a man and in a beast; the descent of stones in Europe and in America; the light of our culinary fire and of the sun; the reflection of light in the earth, and in the planets.
3.The qualities of bodies, which admit neither intensification nor remission of degrees, and which are found to belong to all bodies within the reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever.
For since the qualities of bodies are only known to us by experiments, we are to hold for universal all such as universally agree with experiments; and such as are not liable to diminution can never be quite taken away. We are certainly not to relinquish the evidence of experiments for the sake of dreams and vain fictions of our own devising; nor are we to recede from the analogy of Nature, which is wont to be simple, and always consonant to itself.

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I found some very new GCSE KS4 data. Do note though that the pass rates since 2014 are not comparable to previous years since they changed some rules to the sampling, excluding certain subjects and stuff like that. Also more students of certain groups are taking harder ebacc subjects now, namely blacks.

However this report contains average point scores per group and also ebacc attainment(the harder course) on page 41. Interestingly black Africans have higher average points score even though they have a slightly lower GCSE pass rate(since they take harder subjects on average) and also have higher overall ebacc attainment. Black Caribs and other blacks have a larger deficit in pass rate but their average point gaps are pretty close to whites and so is their ebacc attainment rate(since they take harder subjects on average). Both gaps for black Caribs and other blacks in GCSE average points are smaller than the one between white Brits and white Irish.

Mixed black and white Africans though are starting to open up a gap on whites in everything, ebacc attainment, average points and overall pass rate.

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Sorry I don't know how to make the image larger. If you can edit it for me then please do.

I found some very new GCSE KS4 data. Do note though that the pass rates since 2014 are not comparable to previous years since they changed some rules to the sampling, excluding certain subjects and stuff like that. Also more students of certain groups are taking harder ebacc subjects now, namely blacks.

We found some Wales PISA scores. There is a ~ 1 SD B/W gap there. Burge, B., & Lenkeit, J. (2015). Additional analysis of Wales’ performance in PISA 2012. Also, recent Dutch Cito scores show about a 0.6 SD Antilles/White Dutch Cito gap. I'll look for the link later.

So the real surprise is the high performance of Black Africans in the UK. But it's not such a surprise since I found more data confirming high performance in the US.

Check out the PIAAC scores of African born individual in the OECD: http://nces.ed.gov/surveys/international/ide/ They perform like Eastern Europeans. Hmmm.... so either (1) pretty selected or (2) heavy psychometric bias with respect to international IQ differences

Can that Dutch Antilles gap be considered a closure from the 0.75SD you mentioned here? https://z139.wordpress.com/2012/04/01/holland-white-black-gap/

Can that Dutch Antilles gap be considered a closure from the 0.75SD you mentioned here? https://z139.wordpress.com/2012/04/01/holland-white-black-gap/

A narrowing, no doubt.

Scores: http://www.onderwijsincijfers.nl/kengetallen/primair-onderwijs/deelnemerspo/cito-eindtoets-basisonderwijs

Distribution: http://educatie-en-school.infonu.nl/examen/129319-wat-is-de-verdeling-van-de-cito-toets-scores.html

Distribution to SD calculator: http://rapidtables.com/calc/math/standard-deviation-calculator.htm

So for 2012: μ = (0×501+1×502+1×503+2×504+4×505+4×506+8×507+12×508+17×509+13×510+24×511+36×512+42×513+54×514+60×515+49×516+81×517+99×518+110×519+129×520+145×521+109×522+172×523+193×524+216×525+233×526+254×527+180×528+285×529+314×530+327×531+345×532+360×533+258×534+391×535+415×536+424×537+435×538+296×539+444×540+449×541+442×542+434×543+409×544+266×545+366×546+320×547+279×548+206×549+287×550) / (0+1+1+2+4+4+8+12+17+13+24+36+42+54+60+49+81+99+110+129+145+109+172+193+216+233+254+180+285+314+327+345+360+258+391+415+424+435+296+444+449+442+434+409+266+366+320+279+206+287) = 535.4364
σ = √( (0×(501-535.4364)²+1×(502-535.4364)²+1×(503-535.4364)²+2×(504-535.4364)²+4×(505-535.4364)²+4×(506-535.4364)²+8×(507-535.4364)²+12×(508-535.4364)²+17×(509-535.4364)²+13×(510-535.4364)²+24×(511-535.4364)²+36×(512-535.4364)²+42×(513-535.4364)²+54×(514-535.4364)²+60×(515-535.4364)²+49×(516-535.4364)²+81×(517-535.4364)²+99×(518-535.4364)²+110×(519-535.4364)²+129×(520-535.4364)²+145×(521-535.4364)²+109×(522-535.4364)²+172×(523-535.4364)²+193×(524-535.4364)²+216×(525-535.4364)²+233×(526-535.4364)²+254×(527-535.4364)²+180×(528-535.4364)²+285×(529-535.4364)²+314×(530-535.4364)²+327×(531-535.4364)²+345×(532-535.4364)²+360×(533-535.4364)²+258×(534-535.4364)²+391×(535-535.4364)²+415×(536-535.4364)²+424×(537-535.4364)²+435×(538-535.4364)²+296×(539-535.4364)²+444×(540-535.4364)²+449×(541-535.4364)²+442×(542-535.4364)²+434×(543-535.4364)²+409×(544-535.4364)²+266×(545-535.4364)²+366×(546-535.4364)²+320×(547-535.4364)²+279×(548-535.4364)²+206×(549-535.4364)²+287×(550-535.4364)²) / (0+1+1+2+4+4+8+12+17+13+24+36+42+54+60+49+81+99+110+129+145+109+172+193+216+233+254+180+285+314+327+345+360+258+391+415+424+435+296+444+449+442+434+409+266+366+320+279+206+287) ) = 9.23462804

right?