Reading is just part of language. Its like the tip of the iceberg when it comes to what kids actually take in.

Stuff to us that is background noise like the radio or conversations in the book store, can be startlingly new to kids.

A more active mind will try to fit it all together.

The context of the word usage is the other half - where it is in the sentence and its role in the meaning of the sentence - also give clues.