Eh, I still dream about school sometimes, and it was as low stakes as it can get for me.
I never studied for anything, never did any homework, and to enter university in Germany I just needed good enough grades to pass high school (Gymnasium). GPA was irrelevant.
Of course, I don't wake up with any cold sweat over it.
For me as well, in the last years of Gymnasium they didn't control homework or even attendance much. I missed many classes in the last 2-3 years, because I preferred to stay at home and get some sleep or whatever. Or maybe it is more that I missed most classes by sleeping in class. Memories are hazy at this point. Which could be one reason that I've started to have these dreams where I notice I didn't attend this particular class all year and it's too late.
In Poland, if you want to get into any university, High School diploma is all you need. However, if you want to go the best ones, or to a popular subject (psychology, computer science) in a mediocre one, you need good grades.
The situation is similar in Germany, where I grew up. You need good grades to study the popular subjects. For mathematics, they took anyone who was willing.
I never studied for anything, never did any homework, and to enter university in Germany I just needed good enough grades to pass high school (Gymnasium). GPA was irrelevant.
Of course, I don't wake up with any cold sweat over it.