In the current climate of high-stakes accountability created under the No Child Left Behind legislation, public schools, including charter schools, are under tremendous pressure to show consistent improvement in student achievement for all students. Students with disabilities present unique challenges to schools attempting to meet Adequate Yearly Progress. An accountability system that relies exclusively on students' ability to meet a fixed proficiency level is now under great scrutiny. Indeed, efforts to pilot an assessment system that measures individual students' "growth" are underway in a number of states.What can be learned from analyzing the achievement of students with disabilities using a growth model? This question became the focus of a study conducted in 4 urban charter schools where growth in reading and math achievement were examined for students with and without disabilities. The challenges with measuring growth in charter environments and implications for policies around accountability are examined. (Contains 4 tables.)