Children's reading skill development is influenced by availability of reading materials, reading habits and opportunity to read. Save the Children's Literacy Boost data have replicated this finding across numerous developing contexts. Meanwhile international large-scale reading assessments do not capture detail on current home literacy. The consistent positive association of reading skills with home-based materials and reading habits and the negative association with chores suggest that in developing contexts, opportunity to read outside the classroom is as important to development of reading skills as opportunity to learn these skills inside the classroom. Without data on home literacy environment, calls for action center only on schools and policies, and thus incompletely address learning and equity. Results of Literacy Boost program evaluations find that participants with reading opportunities outside of schools learned more than non-participating peers. Children from homes without books, without readers and without reading opportunities, as well as struggling girls benefited more from provision of opportunities to read outside the school than did more advantaged peers. With the same teachers, reading instruction quality and limited class time, an enhanced home/community literacy environment generated greater learning. Including indicators of home literacy environment alongside skill assessments, whether large scale or small, can best inform effective support for learning and equity.