The School Store Robbery

The day started off with a bang, the school store was robbed. Just like any other school store they sell notebooks, pens and pencils just your average school supply stuff and of course, you can buy the books you need for your classes. They even have sweatshirts, book bags and other things with the school logo.
Some of the students worked there as part of the school's hands on learning program, I think they get some kind of credit for business or math, but I'm not sure. Anyway, the people involved in this little mystery are Wendy Parker; she was working in the store that morning.
Miss. Lawton, who is in charge of the store she had just opened the store and gave Wendy her duties for the morning.
Mrs. Henderson, she's the school principal and of course, me. There were a bunch of things that just didn't fit the story that Wendy told the police, and now that I think about it they should have been easy to spot.
All the clues are there, why don't you see if you can figure out what really happened that cold, wet morning in February.
To celebrate the publication of Death at Noon a special discount for Marlow's friends is available, just visit her website at http://www.mysterygirljournal.com/landing-page-2/