Begin the year with some light fitness activity leading to an indoor sport, such as volleyball. Spend the first few weeks playing tag, freeze tag or other playground games. Have students jump rope for a few minutes a day. After a few weeks, start teaching volleyball skills. Once the students' skills are up to par, break the class into teams and start playing.
For the second quarter, begin with more intense physical fitness. Start each class with having students run laps around the gym and increase the number of laps each day. You might let them play dodgeball at the end of a good class. After a few weeks, begin teaching basketball skills, a great sport to take you through the winter. Do layup, passing and shooting drills. Eventually, break the class into teams and let them play each other.
The third quarter should take you into the spring. Begin with even more intense fitness activity. Instead of laps, try having the students do sprints at the beginning of each class. You can make this more fun with a beanbag exchange sprint, an obstacle course or a relay race. After a few weeks, begin teaching soccer skills. If the weather is nice enough and you have access to a field, let them play soccer outside. Otherwise, set it up in the gym.
By fourth quarter, the weather should be nice enough to have class outside almost every day. If your students are getting antsy for summer, give them a break by teaching circus arts. Show them how to juggle and form human pyramids. For your final sport of the year, do something that can be played outside, such as softball or ultimate Frisbee. Again, teach students skills for a few weeks and end the year with a softball or ultimate tournament.