ADHD meds alone not enough to help kids learn

So, essentially, ADHD meds help kids remain focused in the classroom and do more homework, but don't improve the acquisition or retention of knowledge as represented by test scores.

There are several possible conclusions (in no particular order):

Classroom focus and homework aren't really instrumental to learning in the first place (merely correlated with it), and ADHD meds are only targeting an inconvenient set of symptoms.

Or focus and homework are instrumental to learning (in a "necessary but insufficient" sense), but ADHD meds also inadvertently disrupt (or fail to fix) the formation and/or retention of longer term memory, skills, and knowledge that is necessary for later successful test-taking.

As above, but instead of disrupting the formation of skills and memories, ADHD meds disrupt (or fail to fix) their retrieval and use during tests.

Or possibly something in between, more subtle, like disrupting the establishment of connections between new and existing knowledge, such that knowledge in isolation (eg. bare facts and even sequential skills) can be both stored and explicitly retrieved, but insights are never gained; what's sometimes called understanding as opposed to knowledge.

A deeper dive into the results of tests may help disambiguate between these, by looking at differences in performance based on types of tests (or test questions), such as pop-quizzes, word problems, essays, and various sorts of multiple choice.