Depends on the circumstances. There are circumstances where using a GPS might be appropriate.
I teach my students to fly by ded reckoning because I firmly believe that this method works. It might not be the best method, but it has worked for over a century and it still works now.
Instructors who, for example, use a GPS to check their position whilst on a navigation exercise such as you describe would at least appear to have little enough faith in the methods they teach that they don't believe they can be sufficiently sure of their position without some extra information. (The same, incidentally, applies to any other navigation aid.)
On the other hand, take the example of an early student, say pre-circuits. The weather is distinctly IMC, so the instructor climbs up to VMC on top and carries out the lesson in clear air on top of the clouds. Now, a large part of the instructor's attention needs to be focused on the content of the lesson. Using GPS as the primary means of navigation now is absolutely the right thing to do, especially moving-map GPS, since this makes the navigation a complete no-brainer, and allows the instructor to focus all his attention on what he is being paid to do - instruct.
There are other examples in between, too. While I was training, shortly after Christmas, my instructor pulled out a portable GPS on one of my nav trips. It was a Christmas present, a new toy which he wanted to play with. He programmed our route into the GPS, and monitored how close to our planned track I was flying - but it was with a sense of wonder of how accurate his new toy was, and nothing to do with his inability to follow my progress on a chart.
And of course it is possible for the instructor to teach the student how to use the GPS as part of the exercise (see one of the current GPS threads in the Private Flying forum), in which case of course it is appropriate to use GPS!
FFF
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