Effective assessment is the cornerstone of the teaching and learning process and a benchmark of teaching competency. P-12 assessment in physical activity can be complex and dynamic, often requiring a set of skills developed over time through trial and error. Novice teachers have limited time to hone an assessment process that can showcase their teaching competence via student learning outcomes. Assessment in physical education can be especially challenging due to large class sizes, dynamic environments, limited class time, and lack of standardized tests for sport, movement and fitness skills. Teacher preparation programs should provide learning opportunities for preservice teachers that aid in the development of assessment competencies. Assessment opportunities and practice at school sites with P-12 students in real-time (i.e., in situ) can expedite the development of measurement and evaluation skills that facilitate novice teachers' success in their own classrooms. This article provides examples of in situ practices.