Knowledge Gap (don't know enough...stuff). Vocabulary Gap (don't know enough words).
Sarah Tantillo, creator of the Literacy Cookbook, put a new wrinkle in the comments section. With her permission, I've excerpted it here. Sarah writes:
The vocabulary problem is not merely a word gap. It’s also an explanation gap.
Exposure to fewer words means that one hears fewer examples of complex thinking: fewer sentences, fewer questions, and fewer explanations of ideas or arguments. Hart and Risley...found that parents who explained more also asked more questions and encouraged their children to ask more questions that the parents then had to answer. In other words, children exposed to more words are also exposed to more examples of logical thinking.
The reverse is also true.
Children who communicate with others (like parents) who speak less have fewer opportunities to:
1) build fluency,
2) express and react to ideas, and
3) ask questions and figure things out.
In short, they have fewer opportunities to practice comprehension and logical thinking.
So what's a teacher to do? Sarah writes:
1) Ask “Why?” frequently to elicit inferences and explanations.
2) Use “Think-Pair-Share” to maximize student engagement and give students more experience in explaining ideas—asking them to report what their partners said, so they can practice listening carefully (instead of merely waiting for the other person to stop talking so they can talk).
3) Require complete-sentence responses to ensure that students express complete thoughts and their peers hear these complete models of thinking. Doug Lemov refers to complete sentences as “the battering ram that knocks down the door to college,” and I wholeheartedly agree. More complete explanations—from parents, teachers, and students—could begin to close the Explanation Gap, and ultimately, the Achievement Gap.