Well, then you have folks like my brother who was Kid B, but doesn’t have ADHD and was just a lazy fuck who didn’t see the point of schoolwork. ¯_(ツ)_/¯
The average school is going to be built for the average kid to pass. That means more points are going to be in the day-to-day work rather than the big tests. So if your class has 500 points available and only 100 of those are tests, then yeah, you’re going to fail when you only get 100/500 points.
However, if you have a kid B, then it’s worth looking into if your area has alternate programs from the average curriculum and seeing if they would work for your kid.