R/T is one of those things that can really dent confidence or build it.
There are a few things that leave a lasting impression on students, one is that no matter how the lesson went, if the landing is good, then the student goes away happy. If it's rubbish then a good lesson can be coloured.
Radio work is obviously important, but I prefer to ease people into it so that they don't put R/T too high on the priority list.
The old phrase "Aviate, Navigate, Communicate" is important, so I prefer my students to get to grips with the flying side before distracting them with (seemingly) complex radio procedures.
It is however dependant on the individual, if they have the available capacity, then I'll push them a bit harder and get them to use the radio from very early on.
I like to brief about it early and always get the student to try and preempt any calls to try and build up their situational awareness and confidence, afterall using the radio is all about confidence, more so than many other parts of flying.