If you have a noise reducing sofware, you will be able to bump your iso all the way up 1600 or more if necessary.
I would recommend a monopod or tripod if possible since you won't have the extra f-stops. I would recommend shooting in full manual, making sure your aperture is as wide open as possible. I find I can usually get away with about 1/125 for shutter speed if they are not mocing to fast. However, if they are moving quickly, this will not be fast enough.
Can you provide more information?
Is it an indoor or outdoor performance, a studio shoot, or rehersal shots in the classroom?
Do you know what the lights will be like?
Where will you be shooting from?
Thanks a lot guys!
Pidge:
I will be in a theatre with low lights. I will be allowd to go backstage and wardrobe areas so will have the chance to get more interesting pictures than just on stage.
I don't have the noise reducing software you mention. Which one you recommend?