The present study was conducted to assess the links between in-class use of social media and academic and social school adjustment of high school students attending 9th and 10th grade in Lithuania. Participants included 216 girls and 103 boys aged 14 to 17 years (M = 15.60) attending high schools in the second largest city of Lithuania. Participants filled questionnaires concerning their use of social media during class time and social adjustment at school. Also, schools provided data on current academic adjustment of participants. The results indicated that more time spent using social networking sites during classes was linked to lower grade point average, more missed classes, and poorer relationships with peers.