Teachers' emotional labor is essential to teachers' instructional quality, psychological health, and students' learning effectiveness in classrooms. To assess how teachers manage their emotions to match the display rules of classrooms, this study developed and validated a self-report scale--the Teachers' Emotional Labor Strategy in Classrooms (TELSC)--through three rounds of investigation with secondary school teachers. First, strategies and item statements were collected through existing scales, an open-ended questionnaire, and interviews. Second, the pilot study was conducted, and the results of content validity and exploratory factor analysis confirmed the 17-item formal scale with four dimensions: surface acting, deep acting, expression of naturally felt emotions, and emotion termination. The third round investigated 491 teachers and validated the scale: confirmatory factor analyses verified the four-factor structure; correlations among the four subscales and average variance extracted indicated good discriminant validity; correlations between subscales and emotional exhaustion, teacher efficacy, and years of teaching showed good criterion validity; and Cronbach's [alpha] showed good reliability. Overall, the TELSC scale is an efficient instrument to measure the strategies that teachers use to manage their emotions in classrooms, and it can be applied to understand and improve teachers' professional competence in teaching and emotional interaction.