As a way of clarifying inconsistency in findings related to the personality development of single children and children with siblings in current research. the paper generated empirical models pinpointing causal linkages among background factors, family experience, personality traits and the school performance of Chinese first grade children. Emerging from the data of 850 single children and 566 children with siblings, the close linkages of parental education and occupation with the experience children underwent in families were established and these had profound impact in the first stage formation of positive and negative personality traits and subsequent effects on their school performance. Single children. having closer interaction with their parents, were more dependent and tended to please their teachers by maximizing their positive personality traits and curtailing their negative sides in various aspects of school performance. There were however no significant difference between the two groups in terms of school achievement.