Over the past decade, smartphones have permeated all domains of adolescents’ everyday lives, with research dominated by “smartphone addiction.” This study compares one of the most used measures of smartphone addiction with a new alternative measure, the Smartphone Pervasiveness Scale for Adolescents (SPS-A), which focuses on the frequency of smartphone use at key social and physiological moments of daily life. A sample of 3,289 Italian high school students was used to validate the two constructs and compare their suitability for research on academic performance. SPS-A was moderately correlated with smartphone addiction, showed measurement invariance (across ethnic origins, parental education, and gender), and negatively predicted language and math test scores. SPS-A is a nonpathologizing instrument suitable for analyzing the role of smartphone use in academic achievement in combination with students’ social backgrounds.