Key points are not available for this paper at this time.
Louise B. Miller, Jean L. Dyer, Harold Stevenson, Sheldon H. White, Four Preschool Programs: Their Dimensions and Effects, Monographs of the Society for Research in Child Development, Vol. 40, No. 5/6, Four Preschool Programs: Their Dimensions and Effects (Oct., 1975), pp. 1-170
Miller et al. (Wed,) studied this question.