An instrumental variables approach to assess the effect of class size reduction on student screen time.

An emerging area of research considers links between characteristics of the school setting and health. The existing small evidence base assessing the association between class size and health is inconclusive. This quasi-experimental study uses an instrumental variables approach based on North Carolina's elementary class size reduction policy to assess the relationship between class size and student screen time. Specifically, data are from public school students in North Carolina, USA, who were in 3rd grade any time between fall 2005 and spring 2011. There was no association between class size and screen time (measured as recreational television and/or electronic device use), after accounting for grade size and school size, year fixed effects, and clustering at the school and district level. These findings suggest that, in statewide policy implementation settings, there may not be any immediate spillover benefits of class size reduction policies on student screen time.