This study compares the mathematics performance of pupils who received no day care experiences with those who received mathematics instruction in a structured day care setting, and those exposed to incidentical learning in day care centers. Eighty-six first, second, third, and fourth grade students who had completed four years in a Title I program were studied. Twenty of these students had no formal day care experiences prior to first grade while 33 were exposed to incidental learning and 33 were exposed to a structured program. Subjects' scores on the California Achievement Test (CAT) were analyzed and a comparison of scores among the three groups was made. Results (See Table II) indicate that at the end of each grade, the group which had participated in a structured mathematics program in day care achieved significantly higher grade placement than either the incidental learning group or the group with no day care experience. In addition, at the end of each grade, the incidental group achieved a significantly higher grade placement score than the group with no day care experiences. (Author/MP)