I dunno. Did you ever see Steve Sailer's posts about how bad the PISA scores from Tamil Nadu and Haryana were which made the Indian government refused to participate in it after that? There's almost certainly a lot of cognitive stratification in India, it just seems like the
Caste system is such a strict form of stratification that it there are millions of people who fall into a situation where they are poor/low caste in India but have a lot more potential in a society with more mobility