Effi
Cute question
If you drive a car and cross the street how do your teach your kids not to?
The answer is you don’t.
If parents are justified in sometimes hitting their children then children should know that.
Otherwise what will they think when you hit them.
Part of your chinuch would be to explain to them that a parent has a right to hit their child for chinuch but you can’t just hit because you are angry or don’t get your way.
By the way, to open another whole other can of worms, if someone hits you are you allowed to hit back?