For over a decade, the STEM Teacher and Researcher (STAR) Program has been supported by the National Science Foundation (NSF) Robert Noyce Teacher Scholarship Program along with other funders to provide paid summer research experiences for preservice and early-career science and mathematics teachers at national laboratories and other research facilities. Research into teacher research experiences (TREs) often includes self-report data from program participants, with few studies looking at impacts on students or longer-term impacts. We present results from a set of three Noyce Track 4 Research studies regarding the impact of the STAR Program on teacher effectiveness and productive mind-set. The first study compared eight STAR and non-STAR classrooms and found measurable differences both in how teachers describe their classroom practices and in how students perceive these practices and their own interests and skills, specifically in STEM career awareness, perception of the value of STEM learning, and student perseverance. The second study investigated the impact of STAR teachers on student achievement and found that there were no measurable differences in student achievement on high-stakes state assessments between students of nine STAR teachers and students of other teachers in their five respective districts. The third study found that infusing explicit instruction on productive mind-sets has a positive impact on preservice teachers’ own mind-sets and the strategies that they plan to use with their students. Ongoing work involves investigating the impact of the STAR Program on teacher retention, comparing long-term retention rates of STAR and non-STAR teachers in the state of California. Our work demonstrates the value of supported research experiences for future STEM teachers and illustrates some of the complexity of assessing the impact for students.