Background: School settings offer an opportunity to impact student health and wellness. Quality wellness policies are important in establishing strong wellness environments, but current resources to support policy development, maintenance, and dissemination are lacking. The Building Healthy Schools Program aimed to develop capacity of school districts to improve the strength and comprehensiveness of wellness policies and sustain these activities. Methods: Fifteen school districts in Pennsylvania participated in a program to facilitate the improvement of district wellness policies and practices. Program staff provided technical assistance to evaluate wellness policies before and after program implementation. Professional development and tailored training was provided for school personnel to create sustainability. Statistical analysis was performed to evaluate policy improvement. Results: Thirteen of the 15 participating districts completed a policy revision. Median strength (p = 0.001) and comprehensiveness (p = 0.002) scores improved from baseline to post-program and there were significant improvements in most assessment sub-sections. Some districts were hesitant to make strong language improvements due to their limited capacity (ie, staff) for implementation. Champions (n = 13; 87%) reported confidence to revise wellness policy language independently in the future. Conclusions: Technical assistance provided to districts facilitated significant improvements to wellness policy language, especially in the implementation, evaluation, and communication; critical components for policy impact on school wellness environments. In addition, participant feedback suggested an ability to sustain activities in the future. Both external (ie, technical assistance) and internal resources are needed to facilitate school districts' ongoing wellness policy improvement and implementation, including improved model wellness policy language and enforcement within schools, respectively.