DD is currently in year 10 and doing her art GCSE. She has always loved art and been very good at it (generally gets 9's in her end of year exams etc). She has two different teachers for the subject plus the head of department who pops in often to see how everyone is getting on. She also goes to art classes outside of school with a very good teacher.
Everyone of these teachers can't seem to resist pushing DD into doing things she doesn't want to do or physically taking her pencil/paintbrush or whatever and drawing/painting what they think she should be doing. This tends to make her feel cross and demoralised as she had a plan and feels her picture is no longer what she wanted. I did both GCSE and Alevel art and remember exactly the same thing happening all the time.
Now I appreciate teachers have to teach but surely get another bit of paper and show the technique so the student can try it. Don't do it for them and don't ruin their work. Art is supposed to be self expression not teachers bloody expression.