Final answer:
The major finding of the study by Hart and Risley determined that children from low-income families have significantly lower vocabulary scores than children from high-income families.
Step-by-step explanation:
The major finding of the seminal study conducted by Hart and Risley (1995) determined that children from low-income families have significantly lower vocabulary scores than children from high-income families. After analyzing 1,300 hours of parent-child interactions, the study found that high-income parents talk to their children significantly more, resulting in high-income children knowing almost double the number of words known by their low-income counterparts. This gap in vocabulary and language development contributes to the achievement gap between low-income and high-income children.