There are ways to misuse this general kind of technology. You are seeing it as a cheap doodad that will stimulate a brain area that, when stimulated, improves learning. That's a good thing.

But consider that as research continues, they will probably find that other effects can be achieved by stimulating other brain areas in other ways. Perhaps they will find an area that enhances reading comprehension, or musical ability, or objectivity.

So imagine we reach a state where we have general purpose brain stimulators in most schools, that can be programmed to stimulate the appropriate part of the brain in the appropriate way for a given lesson.

Great, right?

Now consider this. One researcher has already reported that he can induce by brain stimulation a mystical or religious state, where subjects often report feeling they are in the presence of God. If the school stimulators could be programmed for this kind of stimulation, they could turn into a powerful tool for religious indoctrination.

I would not at all be surprised, if the religious inducement turns out to be true (I believe it has not been replicated yet) that they will find other deep emotional things can be induced, such as feeling of national pride and patriotism. I'm sure I don't need to say anything about the potential abuse of that if every public school has a programmable brain stimulator.

This is why we don't throw ethics out the door--we need a way to make the good aspects of this available (boosting memory and math) WITHOUT just blindly getting the bad parts.