Caribbean blacks are Americanized, despite not having the same history as American ones + having a completely different culture. They have taken up the same grievance culture against Whites, preference for ooga booga music, and fatherless culture as American blacks while managing to hate Whitey unless he can give them some tourist dollars while managing to run their countries into the ground in the aftermath of de-colonization. It is absolutely no surprise that they would perform worse, but I doubt there would be that much of a statistical difference if the UK wasn't getting the cream of the crop of sub-Saharan African immigrants.