It is well known that vocal reaction time increases with word length for beginning readers of highly regular languages (transparent). However, little is known about the development of the word-length effect in English readers, a language with highly irregular rules for pronunciation (opaque). The length effect is interpreted as the signature of a reading strategy based on letter by letter decoding (alphabetic reading), and it is extremely large in dyslexic readers of transparent languages. English is thought to be acquired through holistic word recognition, and the word length effect has not been systematically investigated on normal and dyslexic English readers. Here we test the effect of word length on word naming latency for third and fifth grade English average readers. The length effect is present in both age groups (75 ms and 26 ms per letter, R2=0.70 and 0.88 respectively) and surprisingly similar to that found in age-matched Italian readers. Contrary to what is generally thought for English reading acquisition, we conclude that at least up to fifth grade, reading is mediated by a letter by letter decoding strategy in opaque (English) as it is in transparent (Italian) languages. This result is important for understanding typically developing and dysfunctional reading acquisition.