The purposes of this study were (1) to examine whether principles of revision that improve the coherence of text, which have been used successfully on texts for advanced readers, can also be used in revising young readers’ texts; (2) to investigate whether the principles used to revise history texts can be applied to scientific texts and (3) to look at the interaction between text coherence and reading ability. Two authentic scientific texts (on diabetes and on pain) were revised according to four revision principles, providing argument-overlap, making implicit concepts explicit, changing order of sentences and paragraphs, and adding macro-structure to the text. Ninety-one 6^th-grade students were divided into low-ability and high-ability groups and randomly assigned to read either the original texts or the revised texts. Participants’ comprehension was measured by free recall, questions assessing knowledge of the textbase (which assessed a shallow level of comprehension), and inference questions (which assessed a deep level of comprehension). Results indicated that young readers’ comprehension was superior when the coherent version of the texts was read. High-ability readers performed better than low-ability readers. A significant interaction between text coherence and reading ability emerged on the inference questions for one of the texts. That is, low-ability readers’ performance on the inference questions was better when the text was coherent, whereas high ability readers’ performance was not improved by making the text coherent. Thus the text coherence affected the deep comprehension level of these low-ability readers. This finding is discussed in terms of its educational implications.