There's only so many hours you can reasonably expect children (and they are children) to concentrate on schoolwork and although there are some countries where they're cramming for hours and hours a day, I don't think that's "good" for their well-being.

Having (here) such a wide curriculum in the school week means the core subjects don't get the time spent on them that's really needed.

Although it's considered that all children should be taught equally, surely by the time of early teens, some teaching ought to be "on ability"?