Here are some ideas to perk up your morning P.A. announcements:
If you play the national anthem, have a contest for individuals or classes or clubs to sing the anthem. They submit their recording and it becomes one of the versions that you play for announcements.
Have a Call of the Day contest: At the end of the announcements call upon a home room or individual picked at random to answer a trivia question based on that morning's announcements (what was the score of the Jr. Basketball game?) Award prizes for correct answers.
Invite mystery guest announcers: perhaps one of the custodians wants to play DJ for the day or have the History teacher read a blast from the past.
Get a CD that is called TV Toons. Have a Couch Potato Contest with the winning homeroom identifying the TV Toon snippets for the week.
Dave Conlon