This research aimed to develop and evaluate an Information System for Personnel Management (ISPM) tailored for schools under the Surat Thani Primary Educational Service Area Office. Employing a research and development (R&D) methodology, the study was conducted in three phases: (1) a needs analysis through in-depth interviews with 12 school administrators to identify problems and system requirements; (2) system development using the System Development Life Cycle (SDLC) model, followed by expert validation from seven IT professionals; and (3) implementation and effectiveness evaluation with 17 school personnel over a one-month trial. Results from Phase 1 indicated fragmented and inefficient practices, with most schools relying on manual or semi-digital tools. In Phase 2, the developed system was rated highly appropriate across dimensions such as data security (M = 4.95, SD = 0.53) and usability (M = 4.83, SD = 0.38). Phase 3 findings confirmed the system's effectiveness, with an overall satisfaction rating of M = 4.82 (SD = 0.37). The study contributes to the field by offering a full-cycle model of ISPM development grounded in actual school needs and validated through expert and end-user feedback. Limitations include the restricted trial scope and short duration, suggesting the need for future research on scalability and long-term use. The system provides a practical solution for enhancing personnel data management in Thai schools and potentially across broader educational contexts.