Participants in this arm receive the identical 6-week psychological literacy curriculum, but delivered by trained school psychology teachers through traditional face-to-face classroom instruction. Each weekly session lasts 45-60 minutes and follows the same structure and content as the virtual agent arm, including the same four thematic modules. Teachers use standard pedagogical methods such as lectures, group discussions, role-playing, and worksheet activities. This arm serves as the active control condition, representing the current standard of school-based mental health education in China.

Participants in this arm receive a 6-week psychological literacy curriculum delivered entirely by an AI-powered virtual digital agent. The program consists of weekly 45-60 minute interactive sessions aligned with China's national guidelines for mental health education (e.g., Guidelines for Mental Health Education in Primary and Secondary Schools, 2012). The content covers four core modules: (1) psychological foundations and self-awareness, (2) stress and challenge coping skills, (3) interpersonal and communication skills, and (4) healthy lifestyle and future planning. The virtual agent uses scripted but adaptive dialogue, emotion-aware responses, and multimedia engagement to deliver the same evidence-based curriculum used in the control arm. Sessions are conducted in a classroom setting using school-provided computers.

This intervention delivers the identical 6-week psychological literacy curriculum as the virtual agent arm, but through standard face-to-face instruction by certified school psychology teachers. Teachers follow a detailed manualized lesson plan covering the same four thematic modules and learning objectives. Sessions include traditional pedagogical techniques such as didactic teaching, group discussion, role-playing exercises, reflective writing, and in-class activities. Each session lasts 45-60 minutes and occurs weekly in the regular classroom setting. Teachers are trained to adhere to the protocol to ensure content equivalence with the virtual agent condition, though minor natural variations in delivery style, pacing, or classroom interaction may occur. This intervention represents the current standard of practice for school-based mental health education in China and serves as the active control condition.

Mental health literacy is assessed using the UMHL-A (Adolescent Mental Health Literacy Scale), a validated Chinese-language instrument that evaluates two key domains:

Part A: Knowledge and understanding of mental health concepts, common psychological problems, risk/protective factors, and help-seeking resources.

Part B: Attitudes toward mental health issues and behavioral intentions to seek help or support others.

Higher total scores indicate greater mental health literacy. The scale has demonstrated strong reliability and validity in Chinese adolescent populations.

Depressive symptoms are measured using the PHQ-9 (Patient Health Questionnaire-9), a widely used 9-item self-report scale that assesses the frequency of core depression symptoms (e.g., low mood, anhedonia, sleep disturbance) over the past two weeks. Each item is scored from 0 ("not at all") to 3 ("nearly every day"), yielding a total score from 0 to 27. Higher scores indicate more severe depressive symptoms. The Chinese version has established reliability and clinical utility.