In public school classrooms across the United States, approximately one in ten students is learning English as a second language. These students, often referred to as English language learners (ELLs), comprise one of the fastest growing demographic groups in the United States, with approximately 5 million ELLs enrolled in public schools across the country. The majority of ELLs, however, do not exit high school with the proficiency they need to succeed, and standardized outcomes even at the elementary level show the beginnings of a discrepancy between ELLs and their native English-speaking counterparts. This troubling literacy achievement gap is particularly evident in the domain of writing and persists even after students have had several years of supplemental language support. This study seeks to address the writing gap and assessment issues by administering a dual language writing assessment designed for ELLs. The assessment was selected to meet the need for a multifaceted writing assessment that was normed and validated specifically for upper elementary Spanish-speaking ELLs. The study seeks to analyze in detail the writing of intermediate ELL (grades 3-5) in order to determine how the features of their writing differ from those used by native English speakers and the writing features students display in their native languages that maybe overlooked by English-only writing assessments. The purpose of study, however, is not to identify perceived errors, but rather to add to the understanding of second language writing for native Spanish-speaking upper elementary school students. Results of the study have wide-ranging pedagogical and cultural implications that could help inform instruction, educational policy, and teacher education as they relate to the writing assessment and instruction of multilingual learners in increasingly diverse classrooms. [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.]