Ok so I've shot a few college dance shows before, and they are a pain in the
ass. I don't know if kids performances are as painful, but here are some
tips that might apply:
1. Scenes change, lighting change, constantly check your photos to make sure
you are not over/under exposing.
2. Red light is your enemy, but I doubt kids performances will saturate the
stage with red light like dance performances.
3. Shallow depth of field/wide open aperture might sound like a great idea
due to the low light conditions, but if the performers are moving a lot then
getting accurate focus will be very painful. Try to sacrifice some shutter
speed for a narrower aperture. 1/60 should be fine if your hands are
relatively steady.
4. Don't be afraid to crank up the ISO, fixing grain in post is better than
not being able to use the shot due to slow shutter speed and handshake. 1600
, heck even 3200 is doable.
5. Anticipate movements. Again this applies more towards dancing, but
dancers usually tense their muscles before they jump or make any other
flashy moves, and you can see their leg muscles move. I just realized kids
probably didn't grow muscles yet, so never mind. But do anticipate movement
via other means.
You know what, I just thought of this question: What kind of performance is
your kid doing? That matters a lot in our answers.