Teacher training is an important determinant of learning and the overall quality of education. In order to evaluate the empirical evidence from 2010 to 2025 regarding how teacher education and professional development impact classroom practice and student achievement in settings similar to India, this literature study synthesized research on pre-service and in-service teacher education, pedagogical content knowledge (PCK), mentoring systems, and competency-based reforms. The results indicate that effective, continuous training leads to an increase in teacher competency, pedagogical integration, and reflective curriculum behaviour, which in turn leads to improved student learning. However, relatively weak institutional conditions, a lack of follow-up, and disequilibrium in policy implementation often reduce these measures to half-realized efforts. A primary conclusion of this paper is that credential-centric systems of preparation must be replaced by continuous, contextualized, and focused professional development directly related to classroom performance. Initial teacher training curricula should be outcome-driven, with mechanisms embedded into the wider cultural contexts of schools. For India's National Education Policy (NEP) 2020 initiatives, such as the Integrated Teacher Education Programme (ITEP) and Samagra Shiksha, to succeed, professional development cannot rely on isolated, one-off awareness initiatives.