Several good ideas for the destruction scene came up in this thread, and some combo of the three is worth it.
First of all, are any of Carrie's lines in the scene really necessary? I mean, think about it, she's already a fish out of water who's become the geeky-girl-turned-prom-queen of so many teenage movies (witness "Not Another Teen Movie" to prove my point). Why would she want to say anything? "If it's just a dream, I don't wanna wake up!" is the catchphrase here. Maybe some voice-overs, however cheesy that sounds in theatre when it works so much better in film, if she has thoughts that REALLY need to be expressed. So no mic hooked on at that time, and therefore no risk, as would have been inherent with Linzi in the original run. Having eliminated that, we move on to the blood itself.
Okay, someone running on stage with cherry ice cream topping and dumping it on her head is out like Sebastian Bach's theatre career. Dousing her from the rafters is key, and since there's no way for the liquid to interfere with any wiring because she's not wearing a mic, it's all set. No problems there, aside from potential lack of visibility, and even that can be fixed by including the gym teacher trying to help her, and maybe getting a little out of the actress' field of vision before the teacher is "pushed away by Carrie's telekinesis".
The need for a more realistic destruction scene than Carrie's laser delirium is immediately apparent. Strobe lights were suggested to convey the feeling that people and objects are being thrown about, but a) strobes look too close to lasers to completely live the previous staging down, and b) any way you try to stage that would be unrealistic. Putting the actors on wires and flinging them about would not only look silly, but one glitch in the programming or rigging could spell disaster in any proscenium theatre.
That's why I say the sequence of events fall like this:
1. Blood dump
2. Teacher tries to help Carrie, is thrown back (entirely different hurdle introduced if we can't fly her)
3. Carrie reflects for a moment (i.e. "They're all gonna laugh at you!" bit in the film when she goes crazy-eyed and silent)
4. I-beams go off, rigged to allow drop
5. Pieces of the walls blow away, with accompanying pyro effects
6. Disco ball "drops" into crowd
7. Black-out with screams, and Carrie in a pin spot smiling with a demented look in her eye
Exact blocking during the scene is someone else's forte, but the way I see it, this is the easiest way to work it out without introducing anything more embarrassing or overdoing it. And even then there are still holes in it.
"There is no problem so big that it cannot be run away from."
~ Charles M. Schulz