This study tests two hypotheses: (1) prekindergarten children who are provided with a personalized program based on individual assessment of their developmental skills will increase their intellectual abilities and will learn at a higher level than children without this program, and (2) these same children will retain their acquired superiority through the first and second primary years. Subjects were 126 first and 103 second year children in matched experimental and control groups. Experimental and control groups were compared on pretests and posttests given each year of the experiment over a span of four years. Findings from the 1969-1970 phase of the experiment are reported along with the final four year findings (1967-1970). Both hypotheses were supported in part. At prekindergarten level, gains from personalized programming were consistent enough to point out that 4-year-old children had responded well to brief daily individualized sessions of work in game-like situations which were geared to development of sensory, language, motor, or cognitive skills. The positive effects did not carry over to the end of the following year. Although the experimental program made no long-range impact on girls, the cumulative impact on boys indicated they outperformed their control counterparts as well as the girls. Some supplementary studies of achievement are reported along with unanswered questions pertaining to children who evidenced developmental lags. (WY)