I know there are many different types of therapy for Autistic people though I never heard of this one. Even if there was such a thing this teacher seemed to be using the "intervention" in the context of a punishment. I don't like to jump to conclusions on emotional stories like this one until I have heard all sides (as sometimes there was more to it then the media reports), but nevertheless something is terribly not right here.
Back when I was in grade school it was the 1980's and teachers still had paddles. (It wasn't just a Catholic school thing as it seemed the public schools were worse. I went to public school up to third grade and mostly Catholic school from 4th grade on.) Luckily as a fairly docile kid I never received any physical punishments (aside from an occasional slap from the good hearted old nuns for sloppy handwriting or something), though I do remember being terrified that the teachers even had paddles. I rarely saw teachers use them, usually they would just pound the paddle against the metal desk until the kid was hysterical but you could tell that even by the 80's they really didn't want to use them. Stories I hear from older generations about the "good old days" were far worse. Even Castor Oil, a rather harsh laxative was used as a punishment at one time.
I'm not against discipline, but within reason. As it is every December the movie "The Christmas Story" was on countless times. I remember the part when the kid says the F word and gets soap put in his mouth by his otherwise loving parents. That was common years ago even though half the time the parents cursed like drunken sailors themselves. Today that would be considered abuse and I was never a big fan of that sort of punishment myself.
Being mildly claustrophobic I can't imagine what it would be like to be put in a duffel bag. It would not even be acceptable to put a normal kid in a bag let alone Autistic. Many Autistic kids have sensory sensitivities to the point that tickling them can seem like torture. I don't know what this teacher was taught and only God knows where her heart was but what this lady did is certainly not therapy and if she thinks it was than she took something severely out of context.