This research study examines how instructional time is allocated while early childhood teacher candidates are present in mentor teachers' classrooms as part of clinically-based teacher preparation. Researchers conducted 44 observations in 16 mentor teachers' classrooms in three public school districts. The observations were quantified and analyzed to shed light on the nature of co-teaching, instructional decision-making, and student-teacher ratios during clinically-based field experiences. The findings reveal that overwhelmingly mentor teachers and teacher candidates use their time together to engage in co-teaching, which creates lower student-teacher ratios and allows for more flexible groupings of students. The study contributes meaningfully to what is known about effective implementation of clinically-based field experiences and suggests implications for positively impacting student learning outcomes.