"general problem solving ability" isn't a real thing. Proficiency in solving, for example, math problems, does not confer the ability to draw conclusions based on evidence in history class. If you require a kid who's already mastered fractions to simply do harder and harder fractions rather than allowing them to continue onward, they will become bored and distracted, and ultimately burned out or resentful of the education system
OK, not general problem-solving ability, but subject-specific problem-solving ability. And I don't mean more tedious problems, but rather those that require self-discovery of non-standard approaches while not relying on any knowledge from further grades. E.g. for maths Olympiad problems exist for at least as early as 3rd grade, it might be possible to figure out something for younger children too.
I don't see why would shouldn't make it a goal to allow more advanced students to learn at a more advanced pace. They shouldn't be held back by the other students
We'll need to get rid of grade system then and let students advance on different tracks independently for that. Might be a good idea, but nobody is going to redesign the whole educational system because someone made an app.
