After introducing and modeling this concept for your students, you will want to caution them not to overdo the sound effects in a single story.
Of course, the natural flow and feeling of a piece can feel interrupted and stilted if this device is overused. But, sound effects make an extremely effective opening to a story and can be used intelligently throughout.
Additionally, the use of sound effects often opens up a whole new world of creativity for students. They start to play with the sound of words and the way that their writing sounds to the reader. This simple writing technique pays dividends with young writers of almost any grade level.
Once your students are off and running with sound effects in their stories, the only problem may be that you can no longer turn to that pile of writing papers to help you drift off on a sleepless night!