I think being more responsible when she gets home is key. When my step son used to live with us he would give me a bullshit answer like "I did my homework in home room." So then I would ask him to see it and then when he couldn't produce it for me, I would ask him to show me the assignments and literally sit with him until he finished it. Now this kid was 16 years old, and this child is only 8--she needs real guidance. Going to live with the father is not going to solve anything, especially since you said he likes to spank unitl all homework is done.