Oh jeez, why am I not surprised. When I worked as a sub, middle school was my least favorite assignment. Those tween years are the worst of them all.
While I feel badly for the aide and do not condone the behavior of the students, she worked long enough with kids to know the number one rule is "Never let them see you sweat." Had she stood the first speaker down with a stern "Sit down and close your mouth," chances are good, nay, excellent, it would've stopped there.
And while inflammatory and far from PC, I believe the kids who did that need not a spanking, but a public caning as do their parents, whose first words to the school officials will likely be "my baby would never do that.' <sigh>
"Knit on, with confidence and hope, through all crises."
- Elizabeth Zimmermann