California's 1980 proficiency law, which is the topic of this report, mandated that each school district was to adopt or construct tests and establish standards for assessing proficiency in reading, writing, and computation on tasks that were necessary to success in school and in life. In order to graduate from high school, a student must have passed the tests (a student who fails once at the middle school level can try again twice more in high school). This report presents findings of several comparative and experimental studies that investigated three aspects of the proficiency assessment: tests, remedial courses, and changes in implementation of the law. The report also offers recommendations to help school district proficiency programs result in more economical, more equitable, and higher quality education. Sections of the report deal with the following topics: (1) an executive summary, which provides results of the statewide comparison; (2) historical background on proficiency testing; (3) national variation in proficiency assessment; (4) California's proficiency law; (5) proficiency assessment methods; (6) initial consequences of proficiency assessment; (7) a comparison of New York and California's solutions to proficiency assessment of basic skills; (8) a report on improving student performance for passing a minimal competency test in reading; and (9) a course-based model for proficiency assessment. (SKC)