I found these two sentences in an ESL textbook that I read: 1. Children may use words that wound. Three-year-olds in nursery schools, for example, may call each other "dumdum." 2. Children can cause emotional hurt to their classmates. By junior high school days, for example, young teenagers may shout out the people they do not like. I wonder what is the rule of inserting "for example" into sentences. In the first sentence, I see that the phrase is put after the subject noun phrase. In the second, I see that it is put after the adverbial phrase of time and before the subject. Thanks for your help!