Personally, I think it's outrageous that parents are doing their children's homework. Not only does it totally miss the point of the exercise, it encourages children to think that cheating (and that is exactly what it is), is not only acceptable, but encouraged by their parents.
Oh, come on Ian - get off your high horse! If the school is still setting relentless amounts of homework just before the 11+ I don't think anyone would blame a parent for stepping in and helping/taking it on for a few days. Some schools that are completely unsupportive of the 11+ have even been known to increase the amount of homework before the tests just to make a political point about the "kids who will cope at GS".
On the wider point of it being "outrageous" that parents are doing their children's homework, I have lost count of the occasions when my children have been set work that is either ridiculously difficult or excessively time-consuming and I had to finish it off. Then there are the days when there just wasn't enough time to get the homework done, but Mr V. V. Strict will give a detention if it isn't handed in the next day, no excuses ...
It is hardly a culture of cheating, it's just a necessity at times.