Micro-credentials are increasingly being adopted across a variety of industries and countries, including the kindergarten through grade 12 education system in the United States, as a way to identify workers with specific skills, knowledge, and competencies. This report presents the results of a study conducted by RAND researchers who investigated the implementation and impact of teacher micro-credentials intended to improve high school science, technology, engineering, and math teaching and learning in Louisiana. The creation, design, and implementation of micro-credentials was undertaken through a collaboration between the Louisiana Department of Education, Louisiana State University, and BloomBoard. RAND researchers designed and executed a randomized controlled trial of the effectiveness of micro-credentials and an implementation study. The study indicated that teachers' engagement with micro-credentials was relatively low and that micro-credentials did not lead to an increase in student achievement. That said, participating teachers reported that the micro-credentials were well aligned with their courses and supported their teaching practice. Study implications include that micro-credential providers and stakeholders should clearly communicate the value proposition and time requirements of micro-credentials to teachers, as well as provide ample peer and asynchronous supports to teachers for undertaking them.