Parents play an integral role in their children's education. While teachers control the classroom environment, it is the duty of parents to apply proper discipline to insure that children follow through in continuing to develop the proper studying and homework techniques that are initialized in the classroom. If parents are negligent in doing this, then they are at fault for their child failing school.
Children may be failing for some other reason. It's not the parents. If it was, then why? Boom, there's your proof. My best friend told me that it's how the teachers teach. Because it's boring, kids won't want to listen in class and they'll fail. The teachers did well in my other classes, but please... I really want to do that in my sixth grade class! Cuz my teacher calls on me and I feel like I'm an dummy whenever I'm called on. So no, it's not the parents' fault.
There are plenty of reasons why a child might fail at school that has nothing to do with parents. Such as learning disabilities, intellectual impairments, attention deficit disorders. Autism spectrum disorders, speech problems, English as a second language, hearing problems, vision problems and so on.
You can't turn around and blame parents for these conditions