Do you know what is meant by "joy grades"? Does it refer to grade inflation (ie nearly everyone getting very good grades)?
The grading has seen a lot of debate over the last 10 years or so from when it changed (IG/G/VG/MVG --> A-F scale). The way things were graded in the old system had national guidelines, but I think teachers were supposed to take a holistic view on the students performance. Essentially, teachers gave an overall grade. With the new system there were two things that were rather unintuitive. MVG was the highest grade in the previous system, but this does not translate well to an A. Under the previous systems a few programmes required MVG in every subject to compete with other students. So as far as I know the new system required a grade "above" MVG. So that is one thing that makes it different. But also, the new grading system should grade you high if you scored high in ALL criteria for that subject. You were only supposed to be able get one grade higher than your lowest criteria. Of course, a lot of teachers thought "Well IG should translate to F, G should be E-D, MVG should be A. And then I'll just grade like in the previous system.". I think this line of thinking has created a lot of joy grades and unfortunately locked a lot of hard working kids out of their fair spot at uni while letting less hard-working people in.
I know some people who barely got into uni from their grades but turned out to be some of the best performers among their peers because they got fair grades while others got joy grades.
It’s kind of a open secret that if you go to a bad school it will be easier to get a good grade to get into university but harder to pass university.
If you are glass-half-empty person, you can interpret is as a sort of implied "if you pick my school (which means I get money) I will make sure your kid get good grades".