This research aimed to: 1) study relationship building between schools and communities under Rayong Primary Educational Service Area Office 1, 2) study the school administrations of these schools, 3) study relationship building between schools and communities affecting school administrations, and 4) create predictive equations for how relationship building between schools and communities affects school administrations under Rayong Primary Educational Service Area Office 1. The sample used in this research was a group of 558 school administrators and teachers in the academic year 2020. The research instrument was a 2-part 5-rating scale questionnaire. Part 1 measured relationship building in these schools, and part 2 asked for opinions about these school administrations. The reliability was 0.97. The data were analyzed by using: average, standard deviation, Pearson’s product moment correlation coefficient and simple regression analysis.