Extremely low grades

The things going on in our lives have a big impact on our school performance. If you are stressed or feeling depressed, or feeling inferior those could certainly be influencing the drop in your grades.
Just know that you are NOT inferior to anyone else at your school. Everyone is unique and has their own special qualities. I don't believe it's possible to be inferior in looks or talents but there is not a look or a talent that's better than another one.
You sound like a very intelligent person. Grades do not reflect intelligence. It sounds like you just haven't discovered an effective way to study. If you get distracted easily, I would suggest taking frequent studying breaks of five or ten minutes each until you feel you can focus again. Everyone has their way that works best for them.
I'm terribly sorry about your experience with the counselor, teacher, and principal. The adults at the school should be trying to help you get back on track, not degrading you. That is very wrong of them and I hope you will understand that nothing they said about you was true. Don't let criticism get to your heart.

I can see why you feel that way with everybody demonizing you like that. I think what needs to be done, is for you to find a tutor who's not even associated with the school to help you out, or somebody with a completely different teaching method. my brother was in the same boat as you. he was in grade 7(yet pushed him through anyways), and couldn't read above a third grade level, and our grandmother,who was a retired teacher, taught him under a completely different method, and by the end of the year, he was reading and writing at a 12th grade level, and even a teacher thought he plagiarized a story he wrote because he became so good at it. he was the same way with studying. you can throw a book down in front of him and demand to learn what the Pythagorean theorem was, but if you did a more hands-on approach, he'd pick up on it and do it well, and even exceed his classmates! i suspect you're the same way. once you get your tutor with the method that works for you, and once you start doing alot better, and even better than some, most,or even ALL than your classmates, there may be some resistance by the higher ups and vein defending of their ineffective methods, in the end, you'll prove to your parents, councilors,principal, and even to your dumbfounded teachers and classmates that you are indeed as smart or smarter than them. as for talents and looks, HA! I bet they're a bunch of prettyboy pansies that a magazine told them to be, but you'll be a different kind of handsome that will end up with a real woman, because they'll hide and cower from the real women out there, and you'll be much happier for it. talent? lol! so what somebody is a football star, or somebody can strap on leotards and dance around. I bet neither one of them can tear down and rebuild a big block chevy motor, or install electrical or plumbing like the joes can, or even do your taxes. the point is, everybody has different talents, and yours are in a field that you're not thinking of right now, or realize are there.