While most children have a large vocabulary—about 13,000 words—at age 6, they have limited ability to understand complicated language structures. From ages 6 to 10, children gradually begin to think in more complex ways. This growth helps them understand and use the nuances and subtleties of language.
Children gradually advance from understanding simple sentences to being able to interpret complicated content within a paragraph. And they advance from writing a few words at a time to composing complex stories and reports. But this age group's language skills are still limited by concrete, "here and now" thinking. Although school-age children understand more than they can express, they do not comprehend a lot of what adults discuss with them. Ask your child to repeat back what you have said. This will give you a sense of how much he or she understands.
Before age 9, most children understand language very literally. They are confused by statements like, "She is as cool as a cucumber" and may think it means a person is very cold to the touch or somehow looks like a cucumber. Around age 10, children develop an understanding of multiple meanings and relationships between words. They start to make sense of a metaphor like "Lila is a real firecracker."
Children who have well-developed language skills tend to have better memories and attention spans. This makes learning easier for them, and children who are successful in school tend to develop a healthy self-esteem. Also, children who have good language skills often make friends more easily than children who have trouble expressing themselves with words.