My daughter joined TGS last September and she has had very little homework. I have been amazed by how little they get. She probably averages about 3 hours a week and as most of it does not have to be in for over a week, she rarely does any during the week. My daughter in Year 6 gets far more homework than her sister and it all has to be in the next day.
I am sure it depends on how quickly you work and possibly how much you get done in the lessons as much of it is finishing off school work, but I cannot possibly see how this could take more than an hour or so each night max.