It is natural tendency for human beings to place the unreachable Eden somewhere in the vague past, when everything had been better: trees greener, sky bluer, people more kind, food tastier, and children politer than they are now. This can be understood in two ways: either the situation in this world really slowly, yet distinctly, deteriorates with every passing year, or it is just the usual longing for the past. And, however alluring the first variant may be for pessimists, it hardly can be so. If we believe in it, we should believe that the happiest people who have ever lived were the cavemen several tens of thousands years ago, who enjoyed all the benefits of the greenest trees, bluest sky, tastiest food and the most polite children in history. Yet, as far as we can know, it was hardly so.
Children represent a kind of subspecies of human race; it is hard for a grown-up to understand them and interact with them – and vice versa, at least partially. To say that children grow worse with every generation is to forget what you were when you were a child and what your peers were like. I daresay that for an average grown-up a child is always something highly disagreeable and uncomfortable to deal with, whatever he or she says. Placing ideal children in the past is just a kind of defense reflex of our psyche.
And, of course, the upbringing is important. If you compare modern-day businessman, educated in the best schools, with the child of an aristocrat of one hundred years ago, you will find no more differences than between the street urchins of the same two periods of time. Children have always been the same and will stay this way.