As an art student in London in 1982, this was common practice. I remember doing a pastel copy of one of Degas' washing nudes at the Cortauld Institute. You would often see art students set up in a museum like that, though I haven't seen that again in many years.
Seeing just this taking place was one of the highlights for me when visiting the Musée d'Orsay last year - seeing people sketch and watercolour in several of the galleries made the museum become so much more alive.
