When I was young, if I got a poor school report, my parents sat down me to find out how I could do better. Today many parents see it as the teachers problem. Some even contact the teacher or someone higher to complain about it.
So what effect does this have on the youth? In the first example, it takes away the need for the child to feel that he (or she) needs to improve his (or her) effort at school. Also, the young person is effectively reliant on parents sort out issues. How is that going to prepare them to face the world as adults? In the second case, the child almost certainly knows they did wrong. When the parent defends them, it undermines the young ones values and respect for authority.
The modern parent has a tendency to over protect their child. It doesn't help them to grow and mature, neither does it teach them the importance of authority in society. In the first case, children end up unable to effectively stand up for themselves, lacking self confidence and even self esteem. The latter could lead to problems working under a boss in business, as well as with the law and police later in life. Youths must be allowed to grow and parents will do this if they make sure their kids face up to life and the consequences of their actions.