If parents want children to be successful at school they must hold the child responsible for all the work that is assigned. If a parent's attitude towards school is negative, so will the child's be negative. Parents must supervise homework and be more persistent at getting the child to do the work. The easiest thing for parents to do is not fight with the child over school and let the child do whatever. In the long run everyone suffers with the greatest tragedy bestowed on the child.
Successful students know different study skills.
For example, successful students know that when the teacher says read chapter 12 it means to read it as if they had to teach it. Other students who are given the same assignment just read the chapter like a novel and leave it at that. They don't go back and question themselves on what they did read. They do the bare requirement and as a result they do average to less than average work. Study habits are important for achieving success in school and if you examine how successful students study and how other students study you will see a clear difference.