A Wealth of Words: The key to increasing upward mobility is expanding vocabulary.

Long article but worth the time, especially if you're a parent (or grandparent).

So there’s a positive correlation between a student’s vocabulary size in grade 12, the likelihood that she will graduate from college, and her future level of income. The reason is clear: vocabulary size is a convenient proxy for a whole range of educational attainments and abilities—not just skill in reading, writing, listening, and speaking but also general knowledge of science, history, and the arts.