What most scholars and bloggers in the IQ world seemed to not know is that by the time these pieces of news were coming out in the media, there were already African nationalities that had overtaken the white average by a significant margin. The reason it seemed that the black Africans were only trying to catch up now was the usual academic tendency of lumping Africans together into one big racial group when other groups were being identified by nationality (e.g. Chinese, Indian, Pakistani, etc rather than “Asian” or “South-East Asian” etc). Grouping Africans into the monolithic “Black African” ethnicity concealed the different experiences of African immigrants from different nations, some of whom had emigrated as refugees from war-torn countries, while others lad left countries that did not speak much English and were thus disadvantaged in the tests. A negative correlation with English as Another Language was evident on both the CAT scores and the GCSE scores.
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As the table above shows, some African nationalities, particularly Ghanaians and Nigerians, score way above the England mean (and the white British mean), while others, like the Somalis and Congolese, score way below (but still not as low as the Portuguese immigrants, apparently). The low scoring African groups are the ones that migrated as refugees and/or could not speak English, besides being very poor. Improvements among the Somalians have been impressive, especially due to programs dedicated to teaching them English.
Although the Chinese and Indians are still very conspicuously above even the best African nationalities, their superiority disappears when the Nigerian and other groups are broken down even further according to their different tribal ethnicities. Groups like the famous Igbo tribe, which has contributed much genetically to the African American blacks, are well known to be high academic achievers within Nigeria. In fact, their performance seems to be at least as high as the “model minority” Chinese and Indians in the UK, as seen when some recent African immigrants are divided into languages spoken at home (which also indicates that these are not multigenerational descendants but children of recent immigrants).
(Be free to read the article in full, which debunks the blacks are dumb as a race etc.)
Nisbett (2012) suggests that high SES individuals are more likely to be able to develop their full biological potential, whereas low SES individuals are likely to be hindered in their development by adverse environmental conditions. The same review also points out that adoption studies generally are biased towards including only high and high middle SES adoptive families, meaning that they will tend to overestimate average genetic effects. They also note that studies of adoption from lower-class homes to middle-class homes have shown that such children experience a 12 - 18 pt gain in IQ relative to children who remain in low SES homes.
A large number of studies have shown that systemically disadvantaged minorities, such as the African American minority of the United States generally perform worse in the educational system and in intelligence tests than the majority groups or less disadvantaged minorities such as immigrant or "voluntary" minorities, as stated by Neisser.
"The differential between the mean intelligence test scores of Blacks and Whites (about one standard deviation, although it may be diminishing) does not result from any obvious biases in test construction and administration, nor does it simply reflect differences in socio-economic status. Explanations based on factors of caste and culture may be appropriate, but so far have little direct empirical support. There is certainly no such support for a genetic interpretation. At present, no one knows what causes this differential."
That being said, if we are going to continue with the whole IQ factor and why blacks as an average tend to perform badly academically…
The explanation of these findings may be that children of caste-like minorities, due to the systemic limitations of their prospects of social advancement, do not have "effort optimism", i.e. they do not have the confidence that acquiring the skills valued by majority society, such as those skills measured by IQ tests, is worthwhile. They may even deliberately reject certain behaviors that are seen as "acting white." as covered by Neisser 1996 and Ogbu 1978, 1994
Environmental factors are also why blacks tend to score lower on the iq test. Environmental factors including lead exposure, breast feeding, (as stated by Campbell, 2002) and nutrition (as covered by Ivanovic, 2004 and Salojee and Pettifor, 2001) can significantly affect cognitive development and functioning. As stated by Qian (2005), For iodine deficiency causes a fall, on average, of 12 IQ points.