Successfully putting an intervention into widespread practice requires—in addition to an effective intervention—an effective implementation. On the basis of the repeated demand for public speaking promotion programs for elementary school children, a corresponding multicomponent training program was recently developed as part of an extracurricular enrichment program for talented children in Germany. The instructional goals were to promote the children's ability to appropriately use public speaking skills and to decrease their speech anxiety. The program was previously evaluated in an efficacy study with positive treatment effects. Herein, we conducted an effectiveness study in which the effects of the speech training program were replicated after it was put into practice (i.e., offered by several instructors). Specifically, 61 children and eight trained course instructors participated in the study, which used a randomized wait-list control group design with repeated measures. We assessed the effects of the training program on students’ public speaking performance (i.e., their ability to appropriately apply nonverbal–visual, nonverbal–auditory, organizational, and language use skills) with video ratings. We evaluated speech anxiety with self-reports. We found positive treatment effects for both organizational public speaking skills and speech anxiety. Thus, the findings revealed that the intervention was partly successful when put into practice. The results of this effectiveness study are compared and discussed with those from the previous efficacy study.