"NO!"

Children need to learn the word "No."  Preferably, they will learn it from their parents.  Parents teach the word "No" with love.  When the child is about to put their hand on the burner of the stove, a parent may scream "No."  They do it out of love.  If a child does not learn the word from their parents, they have to learn it from Vice-principals, police, correctional officers or Judges.  These people do not teach it with love.  Rather, they tend to teach it as a kind of harsh reality.  Either way, you have to learn the word "No."  Therefore, I contend that it is a parent's responsibility to learn how to say it.