JS, I do remember that at 8, my daughters (both took piano at that age) did require a lot of "mom help" just to make any progress at all in practicing. And I, too, am a single working mom. I know you are reluctant to quit... but I have to say that I was as relieved as they were when the piano lessons and daily practice were gone from our lives. I didn't realize how much stress it was adding for everyone until it was gone. I now really value activities where someone besides me does the coaching and pushing, or that they can pursue with less daily supervision
It had become a forced march. In pursuit of a worthy goal, but in the end it was not worth it for us.
Regarding persistence on a goal... I have to say, I don't think transferring pressure to his grades is very realistic at this point (not sure if that is what you are saying, I am just reading your last paragraph above). This is what you care about, not what he cares about. Heck, my 15 year old isn't entirely on board with it all the time, and you will likely just trade one frustrating battle for another. Not saying you shouldn't have some expectations there, but don't expect it to be a lesson in getting something he wants through persistence. It will likely be another exercise in getting what you want. There is a lot to be said for letting HIM pick an activity -- a sport, a musical instrument of his choosing, acting, a science activity, etc. Then you will have better luck with the persistence lesson, I think.
One other thing to note. The activities that my D loves, is passionate about, and excels at are NOT activities she was doing at 8 years old for the most part. They have so many new opportunities to try out new things in middle school and high school. It is not a crisis for an eight year old to not have a deep passion and skill yet. If he is 15 and not latching on to something, then worry. D's current loves are biology and Quiz Bowl. She does other extracurricular activities (Latin, choir, drawing/painting, fencing, tons of reading). She was doing almost none of these things at 8 (she had started choir then, and always loved to read). But she is now VERY good at the things she is passionate about. So there is plenty of time for an eight year old.
