The purpose of this study is two-fold. Firstly the authors examine, given the amount of time allocated to literacy instruction, whether homogeneous grouping helps improve class manageability over the kindergarten year and whether individual students' externalizing problem behaviors will decrease in tandem. Secondly, they investigate whether the joint effects of homogeneous grouping and instruction time on the literacy growth of students at different ability levels depend on class manageability at the beginning of the kindergarten year. The authors selected data for this study from the Early Childhood Longitudinal study, Kindergarten cohort (ECLS_K). The data were collected by the US National Center for Education Statistics in fall 1998 and spring 1999. According to the authors' preliminary results, classes that were hard to manage tended to have a relatively high proportion of disruptive children and tended to be taught by inexperienced teachers. When kindergarten classes spent more than one hour per day on literacy instruction, high-intensity grouping appeared to be more effective than no grouping in alleviating class misbehavior in the spring especially for classes that had been hard to manage in the fall. They did not detect any grouping effect on class manageability when literacy instruction time is no more than one hour per day. These results held regardless of the availability of teaching aide. Furthermore, there was evidence for a significant effect of high reading time in combination with high-intensity grouping in reducing kindergartners' externalizing problem behaviors. They are currently in the middle of conducting the second part of their analysis.