This study explored the use of writing to help students' develop schemata knowledge for algebraic thinking. Eight seventh-grade pre-algebra students participated in a teaching experiment in which they solved algebraic problems related in mathematical structure. The problems involved contexts of growth and change and size and shape. Qualitative data analysis of students' writing indicated that students used all aspects of schemata knowledge--identification, planning, elaboration, and execution knowledge--to solve the algebraic problems. This article provides excerpts of students' writing and descriptions of ways they used these different aspects of schemata knowledge. The findings from this study support both the use of writing and the use of algebraic problems related in mathematical structure to help students develop tools they need to think algebraically.