Right now, my grades are irregular and very unstable.
In elementary school, I did good, got into the best class, and got straight As, because I was under supervision (schoolwork, first, then play, since I get complaints from teacher for daydreaming too much in class). Then, I reached secondary school, my grades plummeted.
Never listened and paid attention to class, unless the subjects interested me or I like the teachers (rare). The teachers bore me, so I usually just daydream/talk my way through classes. And since I have a kick in handing up abstract, weird homework which most teachers fail to appreciate, except for one english-humanities teacher, who adored my work, which made me pay attention during her classes thus getting As in her classes. But when it comes to other teachers, or subjects which I have little interest in, I get scores that varies from Fs (Maths) to As (Geography, even though I literally sleep during lessons, I still managed to get As)
Oh and I like to make hell for the teachers, so I am always blacklisted by them.
And as for NTs I know,
INTP: retained in school for 3 years, since he only comes to school once per 2 week. but he is intelligent (understands that from talking with him), just that he is really lazy and feels that the education system is useless.
INTJ: he too only pays attention to classes that he deems important or interesting which are Maths/Science.
ENTJ: same. we suck in maths and maths is our evil devil that pulls down our aggregate score. and as for other subjects, we are pretty much on par both in grades and laziness.