The purposes of this research were to develop effective administrative strategies, to examine the appropriateness of the strategies, and to develop a strategy implementation manual for Opportunity Expansion Schools in Kalasin Province. The research was conducted in three phases. Phase 1 focused on strategy development and consisted of two steps: (1) drafting the strategies through a review of related documents and research studies, in-depth interviews with seven experts, and multiple case studies of three model schools; and (2) refining the strategies through expert group discussions involving seven specialists. The content validity of the strategies was verified, with item–objective congruence (IOC) indices ranging from 0.80 to 1.00. Phase 2 involved examining the appropriateness of the developed strategies by collecting opinions from 420 participants, including school administrators, heads of academic affairs, and teachers. The sample size was determined using Yamane’s formula, and stratified random sampling was employed. The research instrument was a five-point Likert scale questionnaire. Phase 3 involved developing a strategy implementation manual, which was evaluated for appropriateness by five experts using a five-point Likert scale questionnaire. The statistical methods used for data analysis included percentage, mean, and standard deviation. The findings were as follows: 1. effective administration of Opportunity Expansion Schools in Kalasin Province consisted of five components: administrative leadership, participatory management, personnel management, process management, and strategic planning. 2. the effective administrative strategies comprised five strategies with a total of 23 activities corresponding to the identified components. 3. the overall appropriateness of the effective administrative strategies was at the highest level. 4. the strategy implementation manual was also evaluated at the highest level of appropriateness.
