Children are powerful statistical spellers, showing sensitivity to untaught orthographic patterns. They can also learn novel written patterns with phonological counterparts via statistical learning processes, akin to those established for spoken language acquisition. It is unclear whether children can learn written (graphotactic) patterns which are unconfounded from correlated phonotactics. We address this question by inducing novel graphotactic learning under incidental versus explicit conditions. Across three artificial lexicon experiments, we exposed children and adults to letter strings ending either in singlets or doublets (that share the same pronunciation; e.g., s vs. ss) depending on the preceding vowel. In post-tests, children and adults incidentally generalized over such context-based constraints that varied in complexity. Explicit instruction further benefitted pattern generalization, supporting the practice of teaching spelling patterns, and there was a relationship between explicit learning and literacy scores. We are first to demonstrate that statistical learning processes underlie graphotactic generalizations among developing spellers.