This study attempts to identify different patterns of cognitive growth in kindergarten and first grade associated with selected subpopulations. The results are based upon a nationally representative sample of fall kindergartners who were retested in the spring of their kindergarten year and then again in the fall and spring of their first grade year. Of special interest here is the estimation of the growth rates of subpopulations of children that are often considered to be at risk, educationally and/or economically. This study also investigates whether or not the absence of formal schooling during the summer differentially impacts subpopulations who are "at risk" because they may lack a strong educational support system in the home.