This research examined the needs assessment and development guidelines for participatory school management to enhance academic effectiveness in Provincial Administrative Organization (PAO) schools across Northeast Thailand. The study employed a mixed-methods design conducted in two phases. The first phase involved document synthesis and survey analysis of 383 participants (275 administrators/teachers and 108 school board members) selected through stratified random sampling from 216 PAO schools. The second phase comprised qualitative interviews with five educational experts chosen through purposive sampling. Research instruments included semi-structured interviews, 5-point rating scale questionnaires (reliability coefficients: 0.942-0.980), and guideline evaluation forms. The findings revealed a framework of six components with 17 indicators. Current practices demonstrated high implementation levels ([x-bar] = 3.16-3.19) across all components, with decision-making and trust-building rating highest ([x-bar] = 3.19). Desired states achieved highest ratings ([x-bar] = 4.61-4.64) across all dimensions. Priority needs analysis (PNIModified) identified vision setting as the most critical development area (PNI = 0.459), followed by implementation (PNI = 0.456) and decision-making/trust-building (PNI = 0.455). Based on these findings, development guidelines encompassing six strategic approaches were formulated and validated by nine expert evaluators, receiving highest-level validation ratings ([x-bar] = 4.97-4.99). The guidelines particularly emphasized systematic stakeholder engagement and collaborative leadership practices, providing PAO schools with concrete strategies for enhancing participatory management effectiveness and academic outcomes.