Most 8 year olds are not responsible enough to complete their homework without some parental help or guidance. Most of the schools I have subbed in require a parent signature in students' homework books so parents can't come back at the teacher and say they didn't know about an assignment. Some teachers even go as far as having parents sign off on every piece of homework that is handed in, so parents have to at least glance at the homework. It sounds like your sister just doesn't want to parent and is taking the easy way out by sending her daughter off to live with someone else.