The premises examined in this longitudinal investigation were that specific behavioral characteristics place children at risk for relationship maladjustment in school environments, and that multiple behavioral risks predispose children to the most severe and prolonged difficulties. Aggressive, withdrawn, and aggressive/withdrawn children were compared to normative and matched control groups on teacher and peer relationship attributes, loneliness, and social satisfaction from kindergarten (M age = 5 years, 7 months; n = 250) through grade 2 (M age = 8.1; n = 242). Children's withdrawn behavior was neither highly stable nor predictive of relational difficulties, as their trajectories resembled the norm except for initially less close and more dependent relationships with teachers. Aggressive behavior was fairly stable, and associated with early-emerging, sustained difficulties including low peer acceptance and conflictual teacher-child relationships. Aggressive/withdrawn children evidenced the most difficulty: compared to children in the normative group, they were consistently more lonely, dissatisfied, friendless, disliked, victimized, and likely to have maladaptive teacher-child relationships. Findings are discussed with respect to recent developments in two prominent literatures: children at-risk and early relationship development.