This study examined whether the transition practices implemented in preschool-elementary school pairs contribute to children's academic development during the first year of elementary school. Participants were 398 children who moved from 36 preschools to 22 elementary schools in two Finnish towns. Children were tested in respect to their reading, writing, and math skills in the preschool spring and in the grade 1 spring. The most common practices reported by preschool teachers were discussions about the school entrants and familiarizing preschool children with the school environment and the new teacher. Multilevel latent growth modeling showed that the more the preschool teachers and elementary-school teachers implemented various supportive activities during the preschool year, the faster the children's skills developed from preschool to grade 1 spring. Co-operation over curricula and passing on written information about children between the preschool and the elementary school were the best predictors of the children's skills, although they were the least commonly used practices. The need to restructure the transition to elementary school and the use of multiprofessional resources are discussed.