Now for the really hard part.
Now that you have planned your video, you need to plan how you will shoot the clips you will need for your video. It makes sense to shoot all the scenes that happen in one location at the same time. For example, you may have an introduction videoed in the Headteacher's Office and then a later scene completing the video where you have a final Headteacher message, also videoed in his/her office. It makes sense to video both these at the same time and the insert them in the correct position at the start and finish when you edit the video in Imovie.
Download and print this Shoot Planning Sheet to plan where and when you will shoot each scene.