One aim of moral education is to help society progress from morally imperfect conventions towards more perfect ones. According to a popular view, "reflecting judgment" is the vehicle of this progress. In this paper, I argue that although reflection is important, it is not enough; moral development also requires practical synthesis. Moral development takes place by securing new connections--conceptual, affective, volitional and behavioural--that bring thoughts, feelings, motivations and actions into alignment with higher reason, to instantiate respect for all who are ends in themselves. Constructing parallels from Kant's theoretical philosophy, I identify three kinds of synthesis that are central to moral practice. If I am right, then a key task for moral education is to support the development of these capacities of practical synthesis.