This presentation from the American Association for School Administrators (AASA) conference in February 2010 by Diep Nguyen, and it was titled Leadership for Achievement: Balanced Assessment Systems for Linguistically Diverse Schools. Nguyen argues that improving the achievement of all students, particularly ELLs and students with disabilities, demands as internal assessment and accountability system that yields real evidence of student growth relative to state standards, program goals, and local benchmarks. The session presents the BASIC model (Gottlieb & Nguyen, 2007), a state-of-the-art system that draws on common formative and summative assessments included in a pivotal portfolio. Participants examine how to use data to inform decisionmaking at the classroom, school, program, and district levels. Practical strategies for using data to foster collaboration among mainstream, ESL, bilingual, and special education teachers, and for planning meaningful professional development are highlighted.