Taping the child's mouth shut is like saying the child has no right to speak. (I'm bigger than you are, so I can force you to shut up!!) I don't agree with that.
If you need the children to be quiet to conduct your class activities, tell them to listen, if they choose to continue to disrupt, threaten to take away their play time so you can make up what was lost by their disruption.
Teaches consequences for their actions, and does not make them feel inferior to a control freak.
But, to this day, I think SPANKING the child, correcting him, and giving him a hug, is one heck of a lot less cruel then yelling at him for days.
OK, that is reasonable. But I really don't think this falls into the category of 'abuse'.
I hate to say it but, you are part of the problem that is inherent in modern day schools. This tape is NO big deal, the teacher is older and the children should have no right to speak in class out of turn.