Are The Parents Responsible For Their Own Children's Bad Behaviour?

Yes and no
That is the nature/nurture debate
Skinner is a theorist who came up with this.
He said that we have a blueprint and we develop according to our nature, but then we do behave how our parents bring us up.
The nature nurture debate is ongoing and will probably never be answered, but it does make it clear that both factors place a role.
Not every doctors or footballer child will become successful and not every child growing up in poverty will become a criminal.

The law says that, yes, the parents are responsible for their child's bad behavior. The parent's are responsible until the child reaches the age of 18.

I tend to agree with that. Who else is going to teach the child right from wrong? Who else should be responsible for shaping the child's moral character? Who else should teach the child to respect himself and others as well as other people's property? Who else is going to teach the child to obey the law? Who else should be the one to correct bad behavior (when it occurs at a very young age) and that there are consequences for bad behavior? Who else will teach that there are rules a good person lives by..."Do unto other's as you would have them do to you." Who but the parent's will teach a child that their good name is a valuable gift not to be thrown away on a few moments of stupidity.

In today's society, there is a tendency to give over these teachings to someone else. The parent's want to be a friend and there is nothing wrong with that as long as the child knows that the parents are also the authority figure. A parent's job is to parent, not just play with or give birth to a child. They must guide, and teach, and punish (as is called for). For every action there is a reaction....be it good or be it bad. Yes, the parent's are responsible, but they must teach responsibility to the child as well. At some point in time, the children become responsible for their own actions. A child that has not been taught respect for themselves and others will have a much harder time dealing with life in a honorable manner. Yet, we expect them at age 18, to suddenly be a caring, loving, giving, helping human beings when they have not seen that in the past 18 years of their life. Children must be taught and must have an example set before them if they are to become what we all want for our children....productive, happy, law abiding adults.

Parents cannot be blamed for their children's bad behaviour. Parents can teach their children to behave properly. It is up to the child whether he wants to follow his or her parents advice. The law should be changed because a lot of parents try very hard to shape their children properly but still their children don't want to listen. A child will only listen to somebody's advice when he thinks that the advice is important and te advice will make him a better person.