I bought my youngest a little basic range finder when she was around 16 and some hp5, she didnt quite get into it initially, but last year she decided she would get more dedicated, so I gave her my old nikon fg20 and a 50mm f2 and some HP5 and she has gone through about 7 rolls. Shes turned 21, will occasionally ring me to organise to go out shooting film.
I developed a roll for her during the week, all shots are in focus, shes starting to get better at working the light into the composition.....wont be long before I work her into LF.
I say start them young, get them interested into the physical pictures, Ive done a couple of darkroom sessions with her and often send her postcards of prints Im working on and they may even take it up as they get older.
Heres a few she did with a friend in a field they snuck into, planed it around sunset to get the nice light.