This study presents the methodological and procedural development process of the Digital Age Teaching Scale (DATS), a summative assessment tool designed to measure application of the ISTE Standards for Educators in K-12 classrooms. The theoretical framework of the ISTE Standards for Educators informed the development of DATS, and an 8-step process of applied theory validated 36 items across 7 framework dimensions. The responses of 642 in-service teachers in K-12 and career and technical education informed and validated the instrument. Two-correlation matrix analysis (inter-item and item-scale correlations) showed statistical inter-item and item-scale correlation; two-dimensionality analysis (exploratory factor analysis and confirmatory factor analysis) revealed seven factors for exploratory factor analysis and indicated an acceptable model fit in confirmatory factor analysis; and reliability analysis points to strong overall internal consistencies. All analysis showed adequate psychometric properties, and future studies should focus on shortening the scale.