Incorporating argument writing as a learning activity has been found to increase students’ mathematics performance. However, teachers report receiving little to no preservice or inservice preparation to use writing to support students’ learning. This is especially concerning for special education teachers who provide highly specialized mathematics instruction (i.e., Tier 3) to students with mathematics disabilities (MLD). The purpose of this study was to examine the effectiveness of teachers providing content-focused open-ended questioning strategies, which included both argument writing and foundational fraction content, using Practice-Based Professional Development (PBPD) and Self-Regulated Strategy Development (SRSD) for implementing a writing-to-learn strategy called FACT-R 2 C 2 . We report the relative number of higher-order mathematical content questions that teachers asked during instruction, from among three different-level question types: Level 1: yes/no questions focused on the mathematics content; Level 2: one-word responses focused on the mathematics content; and Level 3: higher-order open-ended responses centered around four mathematical practices from the Common Core State Standards for Mathematics. Within a well-controlled single-case multiple-baseline design, seven special education teachers were randomly assigned to each PBPD + FACT-R 2 C 2 intervention tier. Results indicated that: (1) teachers’ relative use of Level 3 questions increased following the introduction of the FACT intervention; (2) this increase was apart from the professional development training that the teachers had initially received; and (3) students’ writing quality improved to some extent with the increase in teachers’ relative use of Level 3 questions. Implications and future directions are discussed.

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