In self defense it's a pretty clear case to me...
But very occasionally, there may be a time when for discipline all else fails, and a proper spanking is in order (this being the exception, instead of the rule). Likely such a troublesome student's parents would sign a waver ahead of time.
A teacher should lose their job immediately if he/she has struck a student violently with a slap on the wrist or on the face or with any physical punishment. Injury does not promote a learning safe environment.
If a teacher has struck a student they should be subject to the same laws of the city or state as any once else who has violated the law. Physically harming another human being is against the law and the teacher should be arrested for doing this.
If we give teachers the authority to hit students then we can open a can of worms. Not every teacher can be trusted to not abuse their authority in such a situation. Some people do become teachers because they enjoy being able to control others and use power over them. We could be in for major problems with people like this.
In the old days a teacher could get away with it. That's what they did when I was a kid. Before everyone was sue crazy and the entire society hadn't been corrupted by political correctness and liberal wimpiness. When a teacher hit a student he/she got respect, and it never happened again. But again, that was in the good old days when you either respected the teacher or got expelled. These days our schools have gone from the best to the worst in the world, and this is one of the reasons.
Teachers hit kids in India but it is illegal in Canada and the United States Of America. But if the government over reads it and approves it then teachers would be able to hit kids and it wouldn't be against the law and the teachers would be over power in schools and kids would be afraid of going to school.
A teacher who hits a student... Then a student has also a right to a teacher when they do something wrong!
There are way better forms of punishment than hitting anyway. Hitting causes pain and some teachers abuse the trust so they can't be trusted with the trust at all.
First of all, hitting children is a form of humiliation, and the worst thing an individual can do to a child is humiliate him or her. Also, there are teachers that will abuse their power. There are teachers who do so already with the power that they have. Allowing them to hit children opens doors to trauma and more unmotivated students.