The purpose of this study is to provide reliable and valid descriptions of classroom practice for new curriculum guidelines by developing instructional indicators of Language Arts (Mandarin and English) in general senior high school. To transform the description of core competency written in the Curriculum Guidelines of 12-year Basic Education, the “embedded design” of mixed method containing text analysis, multiple case design and survey research, would be adopted to define, develop and measure the instructional indicators. Ways of data collection include interview with teachers in general senior high schools, expert consulting, classroom observation, questionnaires survey. Our works also provide regular reports of policy suggestion to the government based on the annual schedule of National Academy of Educational Research to meet the demands of researchers, policymakers, administrators, teachers, and the general public.