Purpose: The purpose of this study was to explore the extent to which child- and therapy-level factors contribute to gains in speech sound production accuracy for children with speech sound disorders in receipt of school-based services. Method: Data were obtained from 126 kindergarten and first- and second-grade children currently in receipt of speech therapy services in their public school setting. Pretest and posttest measures of spontaneous speech production and language ability were collected at the beginning and end of one academic year. Using a spontaneous speech sample, percentage of consonants correct (PCC) was calculated for each child; a gain score was computed by subtracting the pretest PCC score from the posttest PCC score. The children's speech-language pathologist completed weekly therapy logs during business-as-usual therapy, indicating the frequency, duration, and group composition of services throughout the school year. Results: Results supported that gain in PCC from pretest to posttest was predicted by several child- and therapy-level variables. Children's initial speech sound severity was negatively related to gains in PCC. Our results also supported that the total number of therapy sessions received in a year was positively predictive of PCC gain. Interestingly, the number of individual therapy sessions was negatively associated with PCC gain. Conclusion: Several malleable therapy factors contribute to gains in speech sound accuracy for children with speech sound disorders. Speech-language pathologists should consider how these factors may be manipulated to best tailor treatment to the individual needs of the children on their caseloads.