A.C.
I am no expert, and i really don't know what happens in the mind of a twelve year old, but with ours it's been the same thing. I don't think it's a matter of understanding the importance of the homework. I think it is combination of lazyness, lack of motivation and just a different way of pushing the boundaries. Instead of doing something more obvious like getting a pircing or picking up smoking, some kids just "decide" to not do something as a means to assert their free will; I think they find it empowering. The older they get one can't really force them to study that much or nag them to death, at this age it's their responsibility. But they can't get a free pass either. Loss of priviledges is a MUST. You can't make them feel that school is valuable and important. They always have an excuse that the teacher is boring, that the book is stupid- whatever. You cant change that, but you can provide incentives. In real life, if you dont work hard you dont get paid. No one cares if you like your job. It's a valuable discipline to learn that as the child for whom everything is provided, they need to do their part and do ALL their homework. failure to do so will result in loss of priviledges.
It's the only thing that's worked for us.