After a few shouty lessons, one of which involved me declaring "I can't teach you!" and flinging his music across the room ( ) we agreed to change our ways and he now does as I ask, whilst I don't push too hard - same as I'd be with my other students. It was someone on this forum who made me examine my own attitude and I realised I was being far to tigerish with him, compared to my other students. So maybe watch out for that too.
Now, I love teaching him and he's working towards grade 3 and really enjoying it. He's also composing his own music, which is something I have no hand in although I am helping him learn to notate it - theory lessons disguised as fun!
Good luck with your endeavour.
Ah yes! That one - the shouty lesson. I don't think I ever flung the music across the room, but I did raise my voice, until DD, never one to mince her words, pointed out that I didn't raise my voice to my other pupils. Cue mother *examining her conscience*! So from then on, we progressed with more demure lessons, and daughter happily reached grade 5 with me, and then grade 6 with another teacher. She still returns home and plays the piano, so I don't think I did too much harm.