Oh my goodness!! I just re-read the part of your post re: the art class. My daughter was THE SAME! In her case it was skating, and she begged and begged (and would become FRANTIC if we mentioned cancelling it). She was desperate to skate! Once we got there, however, she wouldn't go on the ice. The teacher would give me this nasty look, like "why are you forcing her?" ...it was so frustrating!! We finally found a solution: we would arrive at least 20, 25 minutes early to give her time to adjust. She had a specific routine that she had to go through each time (ie. walk to the vending machines, sit and sip water, walk to the notice board, etc etc) before she could skate... very OCD-like. She doesn't have OCD, but she does have anxiety.
What if you brought your son early to art class? Allow at least :30 to ease him into the building. It's maddening... but it worked for my daughter. I was so frustrated/exhausted, looking around at all these "typical" 4 year olds who walked quietly in, 5 minutes before class... meanwhile my amazing daughter who had all those early milestones and is so advanced... was SUCH a handful!! sigh.
Ultramarina has a good point - anxiety can cause defiance as they try and obtain control. My daughter's grade 2 teacher was the first one to point this out to me, and I think she hit the nail right on the head.
My daughter's anxiety issues have dramatically improved as she's aged. Suffice to say there has been a direct correlation between her level of anxiety and her level of obstinance and volatility, all of which have decreased as she's matured.
At nine, she's happy, well adjusted, the second youngest in a gr. 4/5 French Immersion split (there are kids in her class almost 2 years older), and she's in the gifted math program. She's finally happy
She still has intensity and hyper-sensitivities, but they resolve SO much faster now. She also has moments of atypical anxiety, but they're isolated and situation-specific, rather than being a constant "dull roar" of nerves.
