This study aims to identify the role of co-teachers and supervisors of learning tools development toward the success of field practice students of professional education teachers at the middle and high school levels. The population in this study were all students of the Middle and High School Level of Professional Education Teacher Class of 2022, Faculty of Teacher Training and Education, University of Mataram. The sample used was students of Professional Education Teachers at the Middle and High School level, including English, Mathematics, and Civics majors, which were taken using a proportional random sampling technique. The variables consisted of the independent variables, which are the effectiveness of assistant teachers (X1) and supervisors (X2) in the development of learning tools, as well as the dependent variable, which is the success of the Field Practice of Middle and High School Teacher Professional Education Students (Y). Thus, the results show that the role of the development of learning tools by assistant teachers and supervisors in the success of Field Experience Practice for Middle School Teacher Professional Education students proved to be effective, with 51.7% for the English Department, 48.7% for the Mathematics Department, and 53.9% for the Civics Department.