A study was conducted involving 213 children who were either in junior kindergarten in 1978 and first grade in 1980 (69 children) or in senior kindergarten in 1978 and second grade in 1980 (144 children). Of these, 76 children had been identified by their kindergarten teachers as "thriving," 80 as "making average progress," and 57 as "not yet thriving." Sixty of the kindergarten children attended regular half-day junior or senior kindergarten, 82 attended alternate full-day junior or senior kindergarten, and 70 attended full-day senior kindergarten programs. Major concerns of the study were the effects of different types of kindergarten programs; differences between children perceived as "thriving,""average," or "non-thriving"; and the stability and predictability of those differences. In general, no differences were found among children as a function of the type of kindergarten program attended, as assessed in kindergarten or 2 years later. Large differences were found between "thrivers" and "non-thrivers" in kindergarten and second grade on a variety of language and academic skill measures, as well as on teacher-related social skills, temperamental characteristics, and self-confidence and self-direction. Kindergarten measures of social and emotional characteristics were more predictive of first and second grade academic skills than the reverse. A major conclusion was that individual differences in temperament--along with related but more environmentally affected differences in self-confidence, self-directive strategies, and social skills--should concern primary teachers in addition to basic skills. (Author/MP)