Use a flash, if indoors, a wide angle and a tele if you have one. Will cover EVERYTHING. Even better if you have a 18-200mm lens. But usually i'll use a tele unless I can get close enough to the subject. Usually these events will produce boring but necessary shots like the p giving a speech or prize presentation. So use your imagination and come up with different angle for these shots and make sure you can capture the expression of the speaker, which is why i use a tele. Not every photo must be vertical or horizontal. Have fun!
From past experience, even with all the light on on stage, i dun know about how powerful your school's stage lights are, most stages are too dark to shoot without flash. Unless of course you shoot at iso 800, 1600 with f2.8 and bigger. I use a 17-50 2.8 and a 70-200 f4. Of course the 70-200 f2.8 is :thumbsup: but i got no $$ and the weight is a killer :hung:. End of the day, make do with what you have. If your lens not big enough, use flash, high iso. If your lens is big enough, then skip the flash and use ambient light and high iso.
Remember, if your pictures are not sharp, most of the time you and your school will have no use for them. Also, please convert your file from 72 dpi to 300 dpi during post processing. This will enable your school to send them direct to the printer for your newsletters and year book for printing at your image's highest resolution.