This dissertation consists of three essays on teach quality. These essays explore the relationship between teaching skills and student learning. I examine this relationship on average, and then investigate how the relationship varies with the characteristics of the teacher, students, and different measures of student learning.In thefirst chapter, ;;Inside the Classroom: Which Teaching Skills Explain Teacher Quality?;;, I study the relationship between teaching skills and student learning. Ifind that stronger classroom behavior management and, surprisingly, decreased teacher sensitivity are associated with increases in teacher quality across multiple specification and different measures of student learning. These teaching skills have important effects on student learning: a one standard deviation increase in behavior management or teacher sensitivity is associated with a 21% increase and a 42% decrease, respectively, in annual student learning. In addition, I find that the effect of teaching skills on student learning varies with teacher quality. For example, the teaching skill `challenging students;; is associated with a 52% increase in annual student learning amongst the lowest quality teachers but has no significant effect for median or higher quality teachers.The second chapter, Heterogeneous Effects of Teaching Skills;;, studies how the relationship between teaching skills and student learning varies with student characteristics. Ifind that out of 18 teaching skills measured from impartial observations and a teacher test, 13 are statistically significant across at least one subgroup of students. However, only 4 of these teaching skills `behavior management`, teacher content knowledge, a `positive classroom climate;;, and `errors and imprecision;; are statistically significant both on average and across multiple subgroups of students. In addition, estimates show that there are heterogeneous effects of teaching skills on student learning, across classroom characteristics and across different subgroups of students. For example, `teacher sensitivity;; appears to be particularly detrimental to academically prepared students, especially among more academically prepared white and Hispanic students.In the third andfinal chapter, ;;The Multidimensionality of Teacher Quality: Teaching Skills and Students;; Noncognitive Skills;;, my coauthor and I study how the relationship between teaching skills and student learning varies with the measure of student learning. We first show that teacher quality is multidimensional the teachers associated with higher student cognitive skillsare not the same teachers as those associated with higher student noncognitive skills. We next show that different teaching skills are related to different dimensions of teacher quality. For example, teacher sensitivity is positively related to students;; effort and grit but negatively related to students;; academic test scores. This highlights our mainfinding: the teaching skills that help students develop cognitively are not the same teaching skills associated with students;; noncognitive skills.