Well, this type of behavior happened often in my classroom until I started teaching the editing marks. I modeled three times a week how to revise and edit a simple paragraph. For first graders, I started using 4 editing marks: punctuation, capitalization, spacing and eliminate a letter or word within the sentence. Using this technique, helped my students understand the meaning of a sentence and when it was right to add punctuation marks.
Once your students get the routine of using the editing marks, they can practice what they learned by editing simple sentences during a literacy center.
Here are a few samples you try with your students.