For me, it would be the university and a session when I had to carry over 3 different courses. If I had failed another making it 4 courses, I would have been expelled and I would have to start all over again. I completely lost focus that semester and it affected my grades very bad.
I was bullied quite well but it passed at some point. The worst academic session experience I had was in one of my online classes on zoom. I couldn't understand anything the teacher was going on about for house. In fact, I slept throughout the whole session.
Well, um...I am not trying to sound arrogant but I never took my studies seriously till I turned 15.
According to my mom, thanks to my IQ...I never had to worry too much about my grades... So I would say that first 15 years of my life