What bannhammer? Home brew is completely legal in the US and they can’t just come and take your hardware or devtools away (provided you use the open source ones.)
Don't the flashcarts count as breaking DRM and thus not allowed by the DMCA?
Usually the students would run their programs on an emulator instead of the original hardware (this also means they don't need to be provided with a GBA each).
One does not simply avoid Nintendo’s lawyers by following the law :P