The document describes the development and validation of the Brief Adolescent Smartphone Scale (BASS), a 6-item scale to screen for problematic smartphone use among schoolchildren. The BASS was administered to 441 Hungarian schoolchildren and showed good internal reliability and validity when compared to an established smartphone addiction scale. Younger children aged 9-13 scored higher on the BASS than older children aged 14-18, indicating a need for early attention to children's smartphone habits. Secondary school girls reported spending nearly twice as much daily time on their smartphones as boys.