This report grew out of an effort by the Consortium for Policy Research in Education's (CPRE's) Center on Continual Instructional Improvement (CCII) to extend its evaluation of the usefulness of the concept of "Learning Progressions" for the fields of mathematics and science education, to include literacy teaching and learning. Herein, the authors offer a relatively simple graphic model describing how literate communication seems to work, in order to identify the functions or the dimensions along which change and improvement might be observed as students become more effective and sophisticated in using the tools of literate communication. They go on to consider whether the idea of progressions is relevant to understanding this learning, and, if so, what that implies for instruction. Finally, they offer suggestions about what thinking about literate communication in this way may imply more generally for instruction, for education policy, and for assessment. [Additional funding for this research was provided by Pearson Educational Foundation. This document is a reissue of the May 2017 CPRE Research Report RR 2017-2 under the same title.]