Spirit week is usually held the week before homecoming at high schools and some middle schools around the country. Each day of the week features a different theme. For example, one day may be "Dress up like the '80s" day. Another day may simply feature the school colors. It is hard to change the decorations daily, so most people simply decorate the school in school colors for the week. Still, there are some ways to do this creatively.
Lockers
Create a different decoration for each day of the week out of construction paper, and place it on every locker before school starts. For example, on the Friday before the big game, place a "good luck" football on each locker door. If you have a "dress like a movie star" day, put a big gold star on each locker.
Posters
Have students create posters advertising the special days. You can even make this into a contest, with the winning posters earning prizes or special privileges. You might just want the student-body officers of each grade level to do this, as it would be hard to get the entire student body making posters. Hang the posters in the hallways.
Doors
Hold a door-decorating contest. Challenge each homeroom class to decorate the classroom door in a way that reflects school spirit. This will really dress up the school during spirit week, in addition to being a fun activity that will help get the students excited for the big game.
Hallways and Windows
Drape streamers in school colors from light fixture to light fixture down a hallway, to give it a festive air. Attach balloon bouquets to the light fixtures if they are out of reach of the students. Finally, don't forget the windows. Use window paint to paint school spirit sayings and designs onto the windows.