This paper, which presents a comparison of informal and formal preschool programs, describes the arguments used by proponents of the formal, more structured, teacher-centered programs and the informal, more child-centered, programs. Some of the evidence for the effects of early experience on child development and for the effects of teaching style on children's educational progress is reviewed. The paper describes six experimental preschool programs and classifies them in terms of program structure. Student performance in two of these programs, the re-organized Piagetian Preschool Education Program and the Ausubelian Preschool Program, was compared to student performance in a traditional, informal preschool program. Results of the comparison indicated superior performance in the areas of classification, relations, and conservation by the students in the more highly structured programs. The Ausubelian program, characterized by the highest degree of structure, produced the highest level of competency. Delayed testing after an interim period of six months indicated continued improvement for the Ausubelian students. Consideration of learning processes, teacher training, and parent involvement are also considered important components of this program. Results of the study suggest that formal preschool programs are an effective and efficient form of preschool education. (BD)