Information is provided on the methods, rationale, and tests used by PMDC investigators to obtain data on the status of first and second graders during the first five weeks of the school year. Instruments to assess general intelligence, cognitive mathematical concepts and skills, socioeconomic status, and school environment of students from seven schools in four states are described. Data from up to 279 first graders and 137 second graders are summarized and discussed. Reports of four investigative follow-up studies are also included. (MS)