This study investigated instructional leadership functions and school policy factors that affected implementation of instructional strategies presented in a research-based staff development program for secondary school mathematics teachers in school districts in the Chicago suburbs. The instructional leadership functions included the amount and sources of support teachers received in their efforts to improve instruction. School policy factors included the workload assigned to teachers and the school's instructional supervision and evaluation procedures. A second objective was to test the effectiveness of the training provided in the staff development program by analyzing teacher participation, distribution of class time across various instructional functions, and student engagement in the learning process. After an introductory chapter setting forth the research problem and objectives, the four remaining chapters provide (1) an extensive review of the pertinent literature on instruction, staff development, instructional leadership, evaluation, and teacher workload; (2) an in-depth description of the research methodology; (3) data analysis; and (4) a discussion, based on findings, of staff development program effectiveness and organizational conditions for instructional improvement, along with recommendations for future research. Four appendixes provide instrumentation from the study. (TE)