I would just like to say that I grew up in a household where anything less than a A was not acceptable and I grew up just fine. I was not tramautized in any way for being punished for not donig what both my parents and I knew i was capable of doing. I knew the score and knew what would happen. I took all of those AP and honors courses including chemistry physics and calculus and had a few B's, but I let my parents know when I was struggling and as long as they saw that I was really putting in the effort they were ok with that. I think what it comes down to is evpecting each child to work to his or hwer potential no matter what that potential is. I teach high school and I see the c's and D's that could of been A's and B's that come form parents who "never punish for grades" these parents want to blame everyone else but thier children for the kid's poor performance. In 99% or more of cases the kids are simplt lazy or rebellious they are capable, just chose not to try. To the OP good for you for taking a stand.
I can't imagine punishing my child for anything less than a sub par grade. Encouraging the joy of learning should be priority. Not scaring the crap out of a kid. My A's were born of stress. I suspect I would have soared had I actually been applauded and cheered on. In our lives our viewpoint has played out with everyone achieving to their highest, including the foster children we've dealt with.
Your negative view on parents and children is a sad state as a teacher. Perhaps you don't know everything that goes on in those homes. Where do you get that 99% statistic, or is just pulled out of your...head? Just sayin'
So, would your birthday party been canceled if you pulled a low grade? Not even psychodad would have done that.