What you and the GP are saying is completely in line with the lack of experience in the system needed to teach high aptitude students. Some blame the problem partly on No Child Left Behind, which said everyone needs to pass, but said nothing about those who are well beyond passing. But I think it started way before that. I went through a lot of the educational options, that were later discovered to not work so well. Many are listed here:
https://en.wikipedia.org/wiki/Gifted_education I was tested in 1st grade and the school system said I should go to 2nd, but my mother didn't allow it. That was a mistake. Same thing happened in 8th grade. This time, the school system wouldn't let me progress. I have recently learned this was bad for both me and society, unfortunately.
Likely you and many others here and elsewhere as well, including children of those reading this, which is why I write it. If you have a gifted child, promote them! Learn about their needs and get them the educational resources they and society deserve.
The problems you both mention are the result of forcing gifted students to follow a mass education system. Evidence shows that such students should be in an IEP (Individualized Education Program). Many times, the gifted students also have problems with anxiety, depression, social isolation which makes them what's called "Twice Exceptional" students. Such students are written off, like you were, because teachers can't comprehend why such a bright student would struggle.
Such students are also misdiagnosed with ADHD, aspergers, anti-socialism, etc. A poignant distinction between giftedness and aspergers I just read recently is that the aspergers student is a social outcast and has no idea. The gifted student is a social outcast and feels terrible about it.
I think it's a huge injustice. The minds and capabilities of our brightest are a gift to our society and we are letting the treasures waste away.
I've been struggling a lot lately with a lot of issues and re-discovering the problems gifted people have in society has helped me put it back into perspective. What I and you and probably lots others are experiencing aren't the result of something being "wrong" with you, but rather perhaps too much of a good thing can be a bad thing?
For more info:
http://www.sengifted.org
https://www.sengifted.org/post/can-you-hear-the-flowers-sing...
http://www.stephanietolan.com/gifted_ex-child.htm
http://www.metagifted.org/topics/gifted/adultGiftedness/
http://www.hoagiesgifted.org/gifted_adults.htm
http://www.giftedservices.com.au/adults.html