Belligerence personified

It's wrapped up and parcelled in a squirt that lives with us!!!! I'll give you a clue, it begins with B and ends with n.....
I've tried coaxing, reverse psychology, bribing, quiet talking, encouragement, participation, and resorted to yelling at times. You name it, I have tried it with homework. Ben's mission in life is to get me to do his homework for him & I refuse to do it. If he holds out for long enough, I do more than I intend to. Ben's M.O. with homework is to open the book, harrumph a few times and then start complaining that it's too hard and he can't do it.
We have been staying after school and doing extra math with Ben's teacher a couple of times a week and we went in Ben's school room to wait for Mr R today. We started on his math page and Ben had a melt down about the numbers: he can't do it, what's he supposed to do? You tell me, etc.... Mr R walks in and aliens invade Ben's body. He smiles shyly, his voice gets very soft and he sits there and does everything he is told to do, and actively participates.
I don't know whether to cry Hallelujah or to drop him off in the middle of the highway. Why can't kids be nice to their parents like they can be to everyone else? I have heard it said that they feel comfortable enough with their parents to let their guard down and we should feel good about it.
On the way out to the car, I asked Ben why he couldn't work that well with me and why he's so different with Mr R. His answer? "I just want you to do it for me"