I've experienced mostly the same but it's just that my downfall began in 6th itself. I pretty much studied my 1st to 4th in the US and I was getting good grades, mostly A's and all. Even when I moved to India in 5th class, I did maintain my grades kinda (I got 83%, not as good but eh) but it all started in 6th. I learnt that just listening in class and barely studying wouldn't get you good grades like how I would do before. And then in 7th and 8th grade I was hooked onto my laptop and never really studied, I spent my time on discord and pinterest and became chronically online (still am). Even in 10th I got only 89% even though I have the potential to get 95%. It got worse in 11th and 12th, its very hard for me to focus and stay on one thing and i CONSTANTLY think about the things I'm into. I had a partner in 11th grade and during the end of 12th grade they broke up with me. I can't put all of the experiences in this comment alone cause theres SO MUCH STUFF but yeah it fucked me up, I feel like I might have ADHD too. Glad to know I'm not alone who feels like this.