Learning to read can be slow and cumbersome. Beginning readers are focusing so much energy on simply figuring out the words, they don't have enough energy left to worry about how fluently it sounds, much less use expression. Research shows this lack of expression and fluency can effect comprehension.
If you want to hear your students reading with fluency and expression, they must build their sight word knowledge and practice reading fluently. There are many ways to build fluency. One of which is to practice reading phrases which are concentrated with high frequency words. (You may have heard of Fry Phrases before.)
Jodi over at Fun in First has created a Year's Worth of Fluency Passages that she is giving away! Check it Out! - But I hope I win. She has done all the work for you!