I'm 99.9% certain that this will be OK, but independent verification would be reassuring.
I am an "Intermediate" licence holder in the UK. This means that I am authorised to design and build my own transmitters, or buy one, to a maximum TX power of 50 Watts.
As an "Intermediate" though, I am not authorised to supervise an unqualified "Foundation Candidate" (novice). I don't get that privilege until passing the final exam.
Does it seem OK to practice CQ calls on the "public licence" PMR 500mW channels (with a pair of supermarket walkie talkies) to get my friend trained up. The friend can't make it to the radio club/exam centre on a regular basis.
I will also take my friend to a hilltop and demonstrate it for real... we can get repeaters 40 miles away from Dunkery Beacon on a little 5W Baofeng UV-5R.