An investigation was made of standard, nonexperimentally administered Head Start programs in the Philadelphia School District. Findings replicate and extend past findings that Head Start children more often avoided serious school problems than did control children. Head Start children were less frequently retained as they moved through the elementary grades. In later grades, they had better attendance rates and missed fewer standardized tests than did comparison children. The Philadelphia data also confirm the consensus of past Head Start and other intervention studies in finding little or no lasting effect of early childhood programs on achievement test scores. After a brief introduction to the Philadelphia study in Chapter I, Chapter II describes the data base and explains how findings are presented and interpreted in the report. The principal findings of the Philadelphia study are summarized in the next two chapters; Chapter III concerns students' absences and participation in testing programs, and Chapter IV reports on retention in grade and achievement test performance. Chapter V discusses how Head Start produces lasting effects and considers policy implications of the Philadelphia findings and other research results. (RH)