This research examined the latent developmental patterns for early classroom disengagement among children from some of the most underresourced families in the nation. Based on standardized teacher observations from the Head Start Impact Study, a nationally representative sample of children (N=1377) was assessed for manifestations of reticent/withdrawn and low energy behavior over four years spanning prekindergarten through first grade. For each form of disengagement, latent growth mixture modeling revealed three distinct subpopulations of change patterns featuring a dominant class associated with generally good classroom adjustment, a medial class that varied close to the population average over time, and a more extreme class (about 10% of the population) whose adjustment was relatively marginal and sometimes reached problematic levels. Whereas reticent/withdrawn behavior ordinarily subsided over time, low energy behavior increased. More extreme low energy behaviors tended to dissipate through schooling and extreme reticence/withdrawal became more accentuated, with both types associated with later academic and social problems. Attendant risk and protective factors are identified and mitigating assessment and prevention measures are discussed. (author abstract)