The ability to evaluate “sins of omission”—true but pragmatically misleading, underinformative pedagogy—is critical for learning. This study reveals a developmental change in children's evaluation of underinformative teachers and investigates the nature of their limitations. Participants rated a fully informative teacher and an underinformative teacher in two different orders. Six‐ and 7‐year‐olds (N = 28) successfully distinguished the teachers regardless of the order (Experiment 1), whereas 4‐ and 5‐year‐olds (N = 82) succeeded only when the fully informative teacher came first (Experiments 2 and 3). After seeing both teachers, 4‐year‐olds (N = 32) successfully preferred the fully informative teacher (Experiment 4). These results are discussed in light of developmental work in pragmatic implicature, suggesting that young children might struggle with spontaneously generating relevant alternatives for evaluating underinformative pedagogy.