21. A middle school social studies class includes several English language learners. Before beginning a new content unit, the social studies teacher works with the ESL teacher to informally assess the English language learners' knowledge of key vocabulary and prerequisite concepts related to the unit and then preteach key information as needed. During the unit, the ESL teacher often conducts prereading activities with the English language learners before key reading assignments while the content teacher has all students engage in postreading, small-group discussions of the assigned readings. Throughout the unit, the English language learners maintain individual dialogue journals with the teachers about unit content. These activities benefit the English language learners' English language development primarily by: