Student mental health problems often emerge in high school; however, such problems frequently go unaddressed. Using a time series design, we evaluated the effects of the Strong Teens social-emotional learning curriculum implemented by three school counselors and two school social workers with 28 high school students identified with internalizing symptoms. Decreases in students' self-reported levels of internalizing symptoms were statistically significant following the 12-week intervention, indicating moderate improvement. Participants rated the program as socially valid, though they also recommended ways to improve it. Results coincide with past studies indicating that Strong Teens may help reduce adolescents' self-reported internalizing symptoms.