do believe that parents can give us a lot of important and useful knowledge about moral and ethical rules of life, but it is quite doubtful that any parent can teach its child physics or informational technologies, for example. So in this situation an ordinary school teacher would be quite more efficient.
I agree that parents know their children better than anybody else. So teaching a child something new would go easier if it was done by a parent, who knows how to represent the information better and make it more interesting to draw the child in quicker. Apparently this is very useful feature of any parent as a teacher, especially if a child appears to be reluctant to studies. But any average parent has a very limited range of knowledge in some particular subjects like higher mathematics, physics or chemistry. And when it comes to this point, a specially trained teacher has to step in.
Some people think that teachers do not provide enough attention to their children at school; do not explain as good as it is meant to be explained, and so forth. But we still have millions of pupils who successfully finish schools and pass their entrance exam into a university, which implies that somebody who is keen to learn will do it by all means. I wonder, how a parent, wishing to teach his/her child all those subject required by universities, would cope with it on his/her own without a professional teacher? Even if he/she acquired enough time by quitting his/her job, he/she would first have to learn all those subject his/herself. And it is quite hard work to cope with.
In conclusion, our parents are good teachers in what concerns some basic knowledge or daily life. They know how to explain what is good and what is not good to their children according to their standards. But concerning some peculiar disciplines or sciences they are helpless, that is why there are schools, colleges and universities in all countries in the world.