The cited book has no information on how the surveys themselves were conducted. The book is an overall romanticization of pre-colonial india, and frequently indulges in nostalgia.
The following books have a good overview of education&caste in india.
caste system in india is an evil that persists even today, and is a complex topic.
majority of the indian-origin users on hackernews or people in the IT community are very likely upper castes. see [1]
If you are interested to learn more about the caste system in india it is recommended to get your facts from multiple sources. start from [2]
this is livecoding 3d voxel to solve puzzles. the demo was fun. looks like it'll be released soon.