Often when we read with children we have them read a paragraph. This is a good idea for a child who understands how to read and understands what they are reading. When you have a child who word calls and appears to read but does not understand what is being read this often does not work. Word calling is not reading and is often mistaken for reading. To teach this without constantly saying, "You forgot the period." requires a different method.
Each sentence is a complete thought. These thoughts are not complete but run on sentences if the periods are ignored. Sometimes they are just words with no connection to each other.
With a struggling student, I read a sentence and then they read a sentence. I let them chose who goes first. As much as I can I try to let them be in control. When they forget to stop at the period, I gently ask if they are taking my turn. Sometimes, I just say, "My turn, my turn." This makes it more fun than "You did it wrong." Then when they get the process, I accidently keep reading when it is their turn. It is fun to see them say, "Hey, that sentence was my turn." When beginning this process, sometimes they will tire quickly. When they have read 3 to 5 sentences and they are tired, I will ask if they want me to finish the selection. As they become stronger readers, they read longer. One third grader, who has been told he will repeat third grade in October was so excited last week that he forgot to let me have my turn. He was doing so well that I let him go to see how long he could read. Finally after a page I asked him, "Do I get a turn?"
He laughed and said yes, read 3 more sentences and then let me have a turn. Then we did the one sentence each trade off.