As someone said earlier, this thread just goes on and on..........
But I think there's good reason for that.
I'm another instructor putting in my twopence worth. Chuck's postings make a lot of sense. I agree that, for many students, the "double decker bus" or "looking out of your first floor window" method gives them the required picture and they get the flare height quite quickly.
For others, this doesn't work as easily. I was one of those students myself. What I do, and what I teach, is to keep focusing on the aiming point whilst using peripheral vision to clock when the surface at the edge of the runway stops being blurry and starts to have texture. This is, for people with normal vision, the "double decker" height. It's difficult to explain in writing but has brought an enormous grin of understanding onto the faces of many students who were struggling to judge the height. When the blurry green at the side starts to look like grass, we level off.
I demonstrate it by firstly flying along the runway at this height and then getting the student to fly along the runway. When this is all ok, we fly a third circuit and flare again. Immediately, we cut power and look at the end of the runway......thereafter see other posts. It seems to work for many students who are passed on to me for "tweaking" when other instructors say that they can't sort out the flare. Hope this helps some of you who may be finding it difficult.
Another thing that seems to help my students is to understand that there are three distinct phases - the approach, the flare and the hold-off - and that we look at different places as we change from one to the other. I belive that if taught well, this will mean that students will learn to judge any runways, not just land on the one they have memorised !
Like Chuck, I'm not saying that I'm right and everyone else is wrong - just explaining what has worked for a lot of people. It will come good for you too in the end - if you persevere. Happy landings.