We found that both content exposure and screen time had independent detrimental associations with school performance. These findings support parental enforcement of American Academy of Pediatrics guidelines for media time (particularly weekdays) and content limits to enhance school success.

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Purpose-To identify mechanisms for the impact of visual media use on adolescents' school performance.Methods-We conducted a 24-month, four-wave longitudinal telephone study of a national sample of 6,486 youth aged 10-14 years. Exposure Measures: Latent construct for screen exposure time (weekday time spent viewing television/playing videogames, presence of television in bedroom) and variables for movie content (proportion of PG13 and R movies viewed). Outcome Measure: Self and parent reports of grades in school. Effects of media exposures on change in school performance between baseline and 24 months were assessed using structural equation modeling. Information about hypothesized mediators (substance use, sensation-seeking, and school problem behavior) was obtained at baseline and at the16-month follow-up.Results-Adjusted for baseline school performance, baseline levels of mediators, and a range of covariates, both screen exposure time and media content had adverse effects on change in school performance. Screen exposure had an indirect effect on poor school performance through increased sensation-seeking. Viewing more PG-13 and R-rated movies had indirect effects on poor school performance mediated through increases in substance use and sensation-seeking. R-rated viewing also had an indirect effect on poor school performance through increased school behavior problems. The effect sizes of exposure time and content on the intermediate variables and ultimately on school performance were similar to those for previously recognized determinants of these mediatorsincluding household income, parenting style, and adolescents' self-control.Conclusions-These aspects of visual media use adversely affect school performance by increasing sensation-seeking, substance use and school problem behavior.