46 Even when children with limited vocabulary manage to acquire basic decoding skills, they still often encounter difficulty around grade 3 or 4 when they begin needing to read more advanced text in various subjects.47 Their vocabulary deficit impedes comprehension and thus their acquisition of knowledge necessary to succeed across the curriculum.48 Clearly, children who hear little or no English in the home would have even more initial difficulty with comprehension in English. To shrink the achievement gap, then, early childhood programs need to start early with proactive vocabulary development to bring young children whose vocabulary and oral language development is lagging—whatever the causes— closer to the developmental trajectory typical of children from educated, affluent families.49 For these children to gain the vocabulary and the advanced linguistic structures they will need for elementary grade reading, their teachers need to engage them in language interactions throughout the day, including reading to them in small groups and talking with them about the stories. Especially rich in linguistic payoff is extended discourse; that is, conversation between child and adult on a given topic sustained over many exchanges.