This study provides psychometric data for the Scholastic Inquiry Observation instrument and 6 years of research data from an inquiry-based professional training program. The rating instrument provides a resource for measuring 16 inquiry-related learning activities based on level of inquiry implementation and level of active student engagement. Observational data at the item level can be useful for inquiry-based professional development programs. Four scale score options are available for inquiry summarization (Inquiry Implementation for Hypothesis Usage; Implementation of Inquiry Communication; Student Engagement in Hypothesis Usage; Student Engagement in Inquiry Communication) and two scales measuring Student Interest and Mastery of Objectives. Comparisons of the types of inquiry most commonly used and those with the highest levels of active participation by middle school students in science and math classrooms are provided.