These listed above are only two articles on the topic of designing an effective elementary physical education program. There are others on the Web. I consulted our school's Athletics director, Omar Boutaleb, who manages the PE for K-12 at my school here in Morocco. He suggested the following points:
1. Younger children do not yet understand cause and effect. They don't get the idea of physics, and do not understand yet the consequences of their actions, making them very accident prone, both receiving and causing accidents. You must be very safety conscious designing activities, especially water sports. Extra watchers and helpers are a huge bonus. Safety equipment (helmets, pads, etc,) is very important with this ...
Challenges and solutions in setting up an elementary physical education program.