The main strength of this study is the use of timely data
collected from large, nationally representative samples to
assess early implementation of a new federal requirement to
increase students’ access to drinking water. Results should be
interpreted in the context of some limitations, however. Data
are cross-sectional, which precludes a causal interpretation of
reported associations. Some measures assessed compliance
with federal legislation, which raises the possibility of social
desirability bias. To minimize this, respondents were guaranteed
confidentiality, but any survey data carries the risk of
some desirability bias. The response rates were calculated
based on standard definitions,34 but were low among elementary
schools. The final analytic data weights were
adjusted to account for school propensity to respond (based
on predictive models using school demographic variables
associated with response vs nonresponse status), but it is
possible that nonresponse bias could have been an issue,
particularly for schools where practices were not well aligned