Much research has been done on how children learn new vocabulary.

	Those traditional vocabulary lists that are memorized with definitions are mostly a waste of time.
	Children learn thousands of new words a year in the primary grades, but not through vocabulary lists.
	They learn groups of words together and they learn meanings gradually, by seeing/hearing the words in contexts that they mostly understand and gradually inferring the meanings and uses of the words.
	Therefore, you might try when you see a word the child doesn't understand adding it to a list, and then searching for instances of a few words each in a variety of different contexts that the child can read next time you tutor.