Understanding why traditional cultures weaken matters because they embody humanity's heritage. Schooling has been singled out as an abrader of traditional culture. We assess whether schooling erodes one aspect of traditional culture: social capital as shown by generosity to people outside the household. In industrial nations researchers find positive associations between social capital and schooling. We hypothesize that in pre-industrial societies schooling will produce ambiguous effects on social capital: it will reduce social capital expressed through labour help but increase social capital expressed through gifts given. Furthermore, we hypothesize that schooling will lower the likelihood of displaying social capital to kin. To test the hypotheses we use 2004 data from a highly autarkic society of farmers and foragers in the Bolivian Amazon, the Tsimane'. To strengthen the inferences we make about causality we use instrumental variables. Participants in the study included all people of 16+ years of age (n = 574) in 13 villages. Social capital included (a) gifts given to people of other households and (b) labour help offered to people of other households and participation in communal work during the week before the day of the interview. Instrumental variables included childhood village of residence and father's writing ability. Contrary to expectations, schooling weakened all forms of social capital, including expressions of generosity toward kin, but results were statistically insignificant. Parameters estimated with standard techniques and with instrumental variables differed in sign and magnitude, suggesting that researchers should correct for the endogeneity of schooling when assessing schooling's effect on social capital. We end by discussing reasons for the weak statistical results.