The purpose of this mixed-methods experimental study was to investigate the effects and social validity of a text structure intervention for reading and writing in upper elementary grades. Fourth- and fifth-grade teachers (N = 11) in three elementary schools were randomly assigned to implement the text structure intervention or a comprehension strategies intervention. The student sample (N = 351) comprised 160 students who received the text structure intervention and 191 students who received the comprehension strategies intervention, across grades 4 and 5. Quantitative measures of text structure awareness, reading comprehension, and writing quality were analyzed using three-level hierarchical linear modeling. Qualitative interviews were analyzed typologically to assess upper elementary teachers' perceptions of the social validity of each intervention. Quantitative results indicated that students who received the text structure intervention outperformed the students who received the comprehension strategies intervention on a measure of text structure awareness, a graphic organizer task, and use of ideas and details in informational writing. Qualitative findings indicated that teachers found the goals, procedures, and effects of the text structure intervention to be socially valid for upper elementary grades.