Using national longitudinal data of students during their 9th and 11th grades, we address popular concerns over screen time activities distracting students' academic pursuits. We examine gender differences in the types of screen time use, expecting the skill-based activity of video gaming to be more common among boys and the socially oriented activity of chatting online to be more common among girls. Following the displacement effect theory we hypothesize that screen time may displace educational activities, limiting time spent on math homework and lowering subsequent math test scores. Results confirm the gendered nature video gaming for boys, while the gendered nature of chatting online is less clear. Despite popular concerns, findings show no appreciable relationship of video gaming and online chatting with hours spent doing math homework. A very weak, negative association was detected between both screen activities and math test scores two years later, being strongest for the videogaming time of female students. Further research is needed on the full spectrum of screen time activities to determine any potential effects during this developmental stage.