We present an information-theoretic approach to modeling childrens performance in a deductive reasoning game. Ourapproach takes cognitive limitations into account to model the interpretability of feedback that children receive during thegame. We use data of thousands of children, 5 to 12 years of age, from a popular online educational learning system. In theDeductive Mastermind game the player seeks to identify a hidden code that consists of a sequence of colors. The playersees a series of proposed codes together with corresponding feedback providing partial information about the similarity ofeach proposal and the hidden code. In Deductive Mastermind games, the proposals are set up such that deductive reasoningleads to a single possible hidden code. The games vary in code length, the number of possible colors, and the number ofproposals, resulting in game difficulties of various degrees.