Is it good for children to enter film industry at a young age?

It is a personal choice and also depends on the personal situation. I would say NO for my children as I want them to have a protected childhood. I see it as a sophisticated form of child labor. A child is child for a reason and there is no need for him to be like an adult. Eventually he will be an adult. But as I said it is my personal say.

Children entering film industries at very young age lead a very hard life. Like any actors, they can't maintain proper timing for sleeping, eating, playing or all routine stuffs children do. They miss their childhood. So personally, I feel that children shouldn't enter film industry at a very young age.

If children are not allowed to enter in film industry than who will play roll of children in movies.

Its very hard so children should not allow to enter film industry at a very young age

Children do not play the role of adults. Neither the adults play the role of a child. Thus, if a story has a child character, then a child artiste has to enact it. If children stopped from joining movies, then many stories will remain untold so baring a child from joining movies will limit the film industry. It all depends upon the parents' wish and nothing more. Yes, many demerits come with the limelight, but that's the nature of such an industry. One has to accept it or refuse to join the movies, but it cannot be a rule that a child should not join the film industry.