Three experiments investigated the effects of rime consistency on reading and spelling among developing readers ranging in age from 7 to 11 years. Experiment 1 found that children read words with inconsistent feedforward mappings between orthography and phonology (O → P) less accurately than consistent words. OP consistency interacted with chronological age, word frequency and age-of-acquisition (AoA). The effect of OP consistency on reading was larger for younger children than for older children and OP consistency had an effect for low frequency words and late-acquired words only. Experiment 2 found an effect of feedforward consistency between phonology and orthography (P → O) on children’s spelling but no interaction between PO consistency and AoA. Experiment 3 showed that the effects of feedforward consistency are independent of feedback consistency. Our results challenge models of reading and spelling that assume feedforward consistency effects are influenced by the frequency of exposure to words only and we suggest that interactions between consistency and AoA depends on the ratio of consistent to inconsistent OP mappings.