Literacy experts emphasize the importance of natural conversations with children, asking questions while reading books, and helping children identify words during playtime. Even these simple principles may be hard to implement, some educators say, because preschool instructors are often paid far less than public schoolteachers and receive scant training. In one study, Robert Pianta, dean of the Curry School of Education at the University of Virginia, found that in observations of 700 preschool classrooms across 11 states, teachers in less than 15 percent of the classes demonstrated “effe...