I experienced the same issues. Gifted and Talented classes, but bored and angry.

With the benefit of a long lifetime, I now understand why. I read too much outside of school, so I was often ahead of the course material. Being able to read very quickly caused me to be annoyed by any lecture or video presentation. I was also cursed with extreme curiosity, which created questions that could not be answered and were skipped past as unimportant.

Like you, I hated school. Unlike most people, I quit when I was sixteen because I could not stand any more of it.