In school, deaf and hard of hearing students (d/hh) are often exposed to American Sign Language (ASL) while also developing literacy skills in English. ASL does not have a written form, but is a fully accessible language to the d/hh through which it is possible to mediate understanding, draw on prior experiences, and engage critical thinking and reasoning (Allington & Johnston, 2002; Vygotsky, 1987; Wertsch, 1991). This study investigates the impact of Strategic and Interactive Writing Instruction (SIWI) on the development of signed expressive language (ASL) and written English. Our analysis demonstrates that a focus on ASL did not detract from students' writing growth in English. Instead, a focus on building ASL and written English proficiency simultaneously resulted in significant gains in both language and writing.