Prior research suggests that high school students often struggle to evaluate online content; however, with support, they can learn to conduct more effective digital evaluations. This study extends our understanding of how students attend to the source of online information and the role instruction may play in changing students' evaluation of online sources. Reporting on the pre- and posttest responses of high school students (N = 420) who participated in an in-school intervention, this study suggests that students made progress in learning to investigate the source of web content and reading laterally. Findings have implications for how educators and researchers support students' development as critical Internet users.