Research shows that having an excellent reading teacher in the classroom is key to preventing reading difficulties. However, teachers often feel unprepared to work with students experiencing reading difficulties. This can be problematic in a school that uses a multi-tiered system of support for students in which the classroom teacher is responsible for core instruction and early reading interventions. This qualitative study examined the influences on elementary teachers' instructional and assessment decisions when teaching reading to students who are experiencing reading difficulties. Data were collected through both survey and interviews and were analyzed using thematic analysis. Five themes were identified that suggest teachers' literacy instructional decisions are influenced by administrators, their knowledge of reading instruction, professional development, their beliefs about using data for instruction, and collaboration. Findings from this study provide evidence that teacher decisions are more heavily influenced by forces when teachers lack a deep understanding of their students or of effective literacy instruction. When this happens, teachers' efficacy is also affected, which research shows can affect student outcomes. Teacher decision-making is supported through professional development on effective literacy instruction and use of data for planning. Teacher efficacy improves with opportunities to work with and learn from colleagues and from having administrators who work alongside them when making literacy decisions. Recommendations for administrators, teacher educators, and teachers are included as well as suggestions for future research.