Historically, both special education and inclusive general education teachers report feeling unprepared to teach writing, specifically for students with high-incidence disabilities (HID) and those considered to be low-performing writers. Unfortunately, in the United States, these student populations are not making adequate gains in their written performance and require high-quality teachers of writing to improve their overall academic outcomes. This exploratory dissertation includes three complimentary studies that analyzed the pre- and in-service training and preparation that special education teachers (SETs) and inclusive educators (i.e., general education teachers) receive for teaching writing and explore the interplay of this training on the instructional practices implemented in inclusive classroom settings. This mixed methods dissertation investigated (a) empirical writing intervention research in which the student's primary classroom teacher serves as the interventionist to examine the impact of teacher training factors on student writing outcomes; (b) the existing literacy curriculum across nationally ranked special education teacher preparation programs (TPP) for evidence of content aimed at teaching writing for students with HID; and (c) the influence of professional development (PD) and preparation on the instructional practices and adaptations for writing utilized by inclusive science teachers. Findings synthesized across the three analyses comprising this dissertation offer substantial empirical contributions including the need for increased and targeted pre- and in-service training and continued support in writing for teachers of students with HID. Ultimately, the outcomes of this dissertation underscore the importance of developing comprehensive training initiatives for equipping teachers with the necessary skills and knowledge to proficiently instruct students with HID in writing across all subject areas. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]