This study examines the impact of drinking water salinity on children's education using a unique and rich dataset collected from eight southwest coastal districts of Bangladesh. Salinity concentration in drinking water is measured at the household level using water samples from households' primary source of drinking water during the summer, wet and dry season of 20014−15. A third of the deep tube-well water samples was found to be slightly (1000 < TDS < 2000 mg/l) to moderately (TDS ≥ 2000 mg/l) saline. Linking the child-level data on educational outcome to water salinity (i.e. TDS level), the study reveals a statistically significant negative effect of excessive salinity on grade advancement for 7–12 year old children. More specifically, exposure to excessive drinking water salinity (TDS > 1000 mg/l) decreases the grade advancement likelihood of 7–12 year old children by 6.7 percentage points. The results remain robust to alternative model and econometric specifications. The adverse effect of salinity on grade advancement does not vary significantly across the gender of the child while poverty, as expected, exacerbates the effect. Impaired cognitive development due to early childhood exposure appears to be the most plausible channel through which the negative effects of excessive sodium consumption permeate to young children's educational deficit. Additionally, poor health of the adults and elevated medical expenditure play a small yet significant mediating role.