The authors conducted design or classroom experiments (R. Gersten, S. Baker, & J. W. Lloyd, 2000) at 2 sites (Pennsylvania and Florida) to test the effectiveness of schema-based instruction (SBI) prior to conducting formal experimental studies. Results of Study 1 conducted in 2 3rd-grade, low-ability classrooms and 1 special education classroom indicated mean score improvements from pretest to posttest on word problem solving and computation fluency measures. In addition, student perceptions of SBI according to a strategy satisfaction questionnaire revealed SBI as effective in helping solve word problems. Results of Study 2, which included a heterogeneous (high-, average-, and low-achieving) sample of 3rd graders, also revealed student improvement on the word problem solving and computation fluency measures. However, the outcomes were not as positive in Study 2 as in Study 1. Lessons learned from the 2 studies are discussed with regard to teaching and learning mathematical word problem solving for different groups of students. (Contains 5 tables and 1 figure.)