<![CDATA[Assessments of adaptive behavior in students with autism often remain limited to individual abilities and do not fully consider the influence of environmental contexts in school settings. This study aims to develop and evaluate the FD ECO-ADAPT instrument, an ecological-based tool designed to assess the adaptive behavior of elementary school students with autism spectrum disorder. The study employed a research and development approach, beginning with a needs analysis through teacher interviews, followed by instrument design based on an ecological framework. The final instrument consisted of 56 items and was validated by experts in special education and psychology before field testing with 39 teachers. We analyzed data using percentage techniques for validity and practicality and Cronbach’s alpha for reliability, supported by corrected item-total correlation analysis. The results showed that the instrument achieved high validity (95% for construct and 87.5% for content), very high reliability (Cronbach’s alpha = 0.987), and high practicality (90.83%). These findings indicate that the FD ECO-ADAPT instrument is feasible, consistent, and applicable in real classroom contexts. In conclusion, the instrument provides a comprehensive and context-sensitive approach to assessing adaptive behavior, bridging the gap between ecological theory and practical assessment needs in special education. Keywords: adaptive behavior, autism, ecological approach, FD ECO-ADAPT, instrument development]]>
