DD doesn't have ADD, but we've seen stuff like this from her on occasion, as well. In her case, it's flatly task-avoidance.
We tried the same strategies with stunningly similar results.
I have no good advice-- just to keep on top of things as needed and periodically back off to see whether or not he's outgrown it.
I finally see the light at the end of this tunnel with DD now that she is 13. We still have the occasional tiff over avoidance (and always with the subject she finds actually challenges her... hmmm), but in general, she has become MUCH more responsible and self-regulating in this regard.
I would assume that with an ADHD child, that process is naturally going to be delayed somewhat-- so scaffolding additional supports (no, PROVE to me that you have done x, y, and z by showing me your work when you finish... if you have been dishonest about your homework tonight, there will be consequence A and B when I find out...) beyond what agemates might need.
This is all so complicated when you begin trying to tease apart what is age-appropriate, grade-appropriate, etc. Bottom line, when the work is distasteful enough to be worth avoiding in the moment, that is how this is going to go, and only knowing that there is someone checking up on him is going to keep it from happening. Even that may not be enough if the avoidance in the moment seems superior to the delayed punishment for the offense.
Really, even NT kids are all over the map on this one at this age.
A lot of them lie about it.
