When a vowel is followed by an R, the sound of the vowel often changes and is said to be controlled by the vowel.  There are three main r-controlled vowel sounds:  the /ar/ sound, as in barn; the /or/ sound, as in corn; and the /er/ sound, as in fern, bird, and curl.  The lessons in this unit are designed to build students’ proficiency in reading and spelling words that contain r-controlled vowels.