Where I am we still use the square circuit, and our aerodrome is located in a CTR, but I have a feeling that students have no concept of how far away they are from the runway. This is really noted when joining from a nav or something like that. Then again, eliptical circuits which we use at night are even worse. I have flown with students that almost fly over the RW on downwind.
So what is the answer? I think students in the circuit are a danger anyway
Have a good one with it!