I think it's a primitive way to deal with things. I think installing the belief that violence can or should be used to demand compliance isn't necessary, and I don't believe it's a teachers role to discipline children, or even touch them.
Even then, how do you draw the line from when it's legal from when it's illegal? What if the teacher is a body builder who can break that board into splinters with a single swing? Do or can you regulate how hard they can swing? Also, what age (which is a shitty way to measure children since they grow and develop so differently), or grade is it no longer appropriate to hit them? What if a student gets held back several times and is much larger than the other students?
Also keep in mind it's not just boys who are disruptive. If you had a daughter how would you feel about a male teacher paddling their ass?
From yet another standpoint, how would it be legally addressed that teachers are allowed to hit children? Does the teacher have to legally justify their whacking some kid to the police? What if you suspect that your child is being abused at school?
I think it's a bad idea.
-wino