If a teacher did that in the UK they would be arrested.
I am not surprised by this video - but I am disgusted. What sort of twisted human being would strike a a five year old little boy with what is basically a cricket bat? Not only are they physically injuring a defenceless child, they are teaching him that it's okay to assault people, and he will also now have an underlying awareness that his mother doesn't have his back because she stood there and (albeit unwillingly) let them hurt and frighten him and didn't help him. The result might then be that he grows up thinking it's okay to hit people or similar, and he will have a mistrust of his own mother and of those in authority - and what sort of adult will he then become because of that? The absolute short sightedness, stupidity and cruelty of it is off the scale.