Many students in the United States struggle to achieve proficiency in writing. Writing is an important skill to develop, as it is a way for students to communicate what they know and integrate knowledge and critical thinking skills. A lack of writing proficiency can have a significant impact on academic performance in secondary school and on postsecondary outcomes. Improving writing instruction requires theoretically sound, scientifically validated teaching practices, including assessments and instructional methods. It also requires that teachers are well prepared to implement such practices, including using assessment data to tailor instructional methods to meet the needs of students who experience significant writing difficulties. The purpose of this chapter is to provide an overview of advances in research and practice related to validated teaching practices designed to improve the writing outcomes of students with intensive needs, and to describe an innovative way to prepare and support teachers to implement such practices. [For the complete volume, "The Next Big Thing in Learning and Behavioral Disabilities. Advances in Learning and Behavioral Disabilities. Volume 31," see ED614920.]