Most of the time, students feel like they must begin at the beginning of their story. They start when they feel the story begins, and follow it through in the "correct" sequence til they get to the end.
However, writers can play with time just like film-makers do. They can begin their story at the end, and flashback to the beginning. They can begin in the middle and go back and forth in time.
For example, if I was telling the story about when I broke my arm, I might begin like this:
I knew I was going to get into trouble. I was sure my mom and dad were going to yell at me when they found out what had happened. After all, what kind of kid falls off the diving board and lands half in the pool and half on the concrete?
That afternoon began like any other summer day. I got on my suit, flipflopped down the railroad tie steps, over the bridge that spanned the creek, and across the bristly-brown grass field to the pool. Staying there til dusk, I went back and forth between the big pool and the diving tank, ate frozen Milky Way bars, alternating dips in the chlorine-filled water with naps on a pool chair. The afternoons seemed to last forever.
Of course, this is an off-the-cuff example. However, beginning at the end, or in the middle, keeps the reader on their toes. They are not sure exactly what the story is about, which might compel them to delve in further...
Having students type or write their story on only one side of the paper, they can then cut it apart into sections/paragraphs. They can then arrange and rearrange the parts until they find a sequence that works for them. Younger students, or struggling writers could even use post-its. Writing one event on each post-it note would allow them to fiddle around with time, and then later, flesh out the story.