This depends on where we are in the training program:
- PPL and in the first few flights before any thought of solo? I'd call for the go around and get instructions to rejoin the circuit. In fact, I might even take control myself and describe to my student what I'm doing and why.
- PPL and approaching solo or just after solo - I'd give the student the option and discuss with them afterward - either how they performed or what needs to happen in that scenario. I'd give examples of where we may have to execute such a maneuver outside of the circuit.
- PPL and just before the cross country work - they should be able to do it, especially if we've had any exposure to mountainous terrain where box canyon turns should have been discussed.
- CPL and after - if they cannot accomplish this simple ask, I'd be tasking them in their next solo flight to go do some steep turns with the maximum allowable flap for a 2g maneuver. Depending on where they will have their first operational job, orbits on base may be a frequent request and they can't just go missed every time ATC asks.