Sounds like your student may not be studying on his own other than a cram session right before lessons. That or he is overthinking every procedure to the point where he cannot process the simple cues needed to land. Those last 50 feet to the ground are more like art, than procedure. We all know you have to feel your way down. Perhaps the student is trying to find some method to use that is one-size-fits-all, instead of guiding the aircraft to the ground.

In terms of solutions, I think the go-around practice could be extremely valuable, especially if the student knows ahead of time that a go-around is coming. There's no worry of having to control the plane to the ground. I used to do several laps down to about 100-200 feet with students so they could get their procedure down. The goal is to obtain an appropriate and stabilized final approach, every time. A good approach gives you the best chance of a great landing.

Once the student masters arriving on final, he can concentrate on the art of landing. Set your student up on glidepath, fully configured, and let him fly the last 500 feet. (Obviously, you should remain close on the controls given the low altitude). Alternately, you can have the student talk you through a landing, performing his instructions to get you on the ground (within reason of course). This may give you a hint as to whether he knows the drill and is having problems with the flying part, or if he does not understand what he must accomplish.