The current study used a programmatic dissemination model as a guiding framework for testing an evidence-supported treatment (EST) for child anxiety disorders in the school setting. The main goal of the project was to conduct the first of a planned series of partial-effectiveness tests (group-design randomized controlled trials) evaluating the impact of a modular, algorithm-driven cognitive behavioral therapy (CBT) program for childhood anxiety disorders with one selected element of the practice setting: the school clinic environment. Forty children aged 5−12 years old with anxiety disorders attending two elementary schools in the greater Los Angeles area were individually randomized to receive the school-based CBT program either immediately or after a 3-month waiting period. The specific aims of the project were to examine the impact of the intervention on diagnostic status and anxiety symptomatology, as well as outcomes relevant to children's daily functioning including social adjustment, academic performance, and health utilization practices of youth. The study also aimed to explore increases in self-efficacy as a potential change mechanism of the intervention. Findings from the present work provided preliminary evidence that the modular, algorithm-driven CBT intervention evaluated in this study was efficacious at reducing anxiety when implemented in the elementary school setting. In comparison to children in the waitlist condition (WL), children who received immediate treatment (IT) experienced greater child and parent reported anxiety symptom reduction and were more likely to be anxiety diagnosis-free according to independent evaluators' ratings at the post-intervention/waitlist assessment. Specifically, 72.3% of children in the IT group met CGI-I criteria for positive treatment response, and 95.5% were free of any anxiety diagnosis at the post-intervention/waitlist assessment. Comparatively, the corresponding figures for children in the WL group were 5.6% and 16.7%. Treatment effects failed to extend beyond target anxiety diagnosis and symptoms to include either internalizing symptomatology or functioning outcomes. Additionally, a treatment effect on self-efficacy did not emerge between the two conditions, which precluded testing self-efficacy as an intervening variable. The results of the current study are interpreted in relation to previous literature. Limitations of the study, strengths of the present work, and recommended directions for future research are discussed.