Early adolescence (ages 11-14) is a key developmental period repeatedly coupled with the onset of mental health problems. Middle schools provide a naturalistic setting in which to implement programming to prevent the development of more significant mental health problems. School-based social-emotional learning (SEL) programs have previously filled this gap and have demonstrated impact on social and emotional skills, attitudes, behaviors, and academic performance. Across SEL programs, emotion regulation (ER) has been identified as a primary component that impacts important mental health and school outcomes. ER, a transdiagnostic correlate of mental health, is the set of processes used to manage feelings and their expression to achieve goals. Among middle schoolers, greater use of ER strategies has been found to protect against negative social effects and poorer mental health. Among SEL programs for middle school students, none have examined the impact on ER or mental health outcomes beyond conduct problems, and many fail to provide adequate training and support to their key implementers, teachers. Implementation is also often hampered by time- and resource-intensive delivery schedules. For these reasons, incorporating brief ER skill-building programs using a digital health model into middle schools that includes teacher training to support learning can reduce mental health concerns and promote school functioning. We propose to optimize a brief, validated, digitally delivered ER intervention (iTRAC; Talking about Risk and Adolescent Choices) to include a teacher component that can be delivered within middle schools. This will improve upon the rigor of our pilot research by implementing the program during the regular school day and developing a complementary teacher program to enhance the uptake of the digitally delivered student-facing program hereafter referenced as iTRAC+. iTRAC+ will be evaluated on implementation outcomes and impact on ER abilities among middle schoolers and teachers. The current study will be carried out across implementation Steps 1-3 and will be guided by the Advancing Children's Connection, Emotion Regulation, and School Support (ACCESS) Center implementation framework. In Step 1, we will work with an expert panel and community partners to develop the classroom and teacher components and identify strategies to enhance teacher and school engagement with the program before advancing to the next step. In Step 2, we will evaluate the initial acceptability and feasibility of the expanded iTRAC+ program with four classrooms for further refinement of teacher training materials, teacher recruitment plans, and the classroom delivery schedule. During Step 3, we will randomize 46 classrooms from four middle schools to receive either iTRAC+ or an attention control condition to examine the preliminary impact on mechanisms and outcomes. Students and teachers will be assessed prior to randomization and 4 months after program implementation. This schedule will permit short-term evaluation of the iTRAC+ program and identify barriers and enhancers to future implementation of the program to be assessed within a fully powered implementation trial (R01).