There is no other way to phrase this. If you hit a child, you are committing an act of violence against that child. Some of the damage can be emotional and mental, but the more severe corporal punishment becomes, the likelihood of physical injury becomes increased. Simple knowledge of rewards and stimuli will go a lot farther than a spanking.
In many cases, corporal punishment goes beyond spanking. The hitting is usually done with a cane, wooden paddle, leather strap, or yardstick. Having this done to you in public or not, can definitely leave an emotional and/or physical scar. It may give the teacher immediate results, but something that can quickly go over the line, isn't worth it.