This segment of the national evaluation study of the Follow Through Planned Variation Model discusses findings of analyses of achievement test data which have been adjusted to take into consideration the preschool experience of children in three Follow Through cohorts. These analyses serve as a supplement to analyses presented in Volume IV-A of the study which did not incorporate preschool experience as a factor. Included are: (1) overview of findings of supplementary analyses; (2) review of models under study and instruments used; (3) presentation of samples under study and comparison of these samples with those in Volume IV-A; and (4) review and discussion of analytic strategies implemented for supplementary analyses. An argument is made for basing the conclusions of the national study on results derived solely from Cohort III-K (the group of children who started Follow Through at kindergarten level in 1971). Three sets of results are compared: those from Cohort III-K only, controlling for preschool differences; those from all cohort streams, controlling for preschool differences only for Cohort III-K; and those from all cohort streams, controlling for preschool differences. Appendices comprise more than 450 pages. (Author/JMB)