If the process of eliminating distractions hasn't yielded positive results, then maybe the solution is to introduce positive distractions. There was a thread here a while back where a number of us admitted that having music or the television going on in the background actually helped us focus on homework, and get it done quicker. For my DD9, the TV would definitely be a problem, but just having me nearby and able to respond to her commentary or questions is enough to keep her focused and on-task.
The issue here is often one of mood management. The child doesn't have an issue with doing school work at school, because that's what that time is for, and she has nothing better to do. At home, there's resentment, because that's perceived as her free time, homework is an unwelcome encroachment, and there are many ways she could be spending that time. So, how can the experience be made less miserable?