Is it, though? Admittedly it's been a while but I feel like once you get beyond the absolute basics of circuitry Minecraft gets ridiculously complicated in terms of building the structures necessary to establish the circuitry (just search YouTube for the monstrosities that are necessary to build simple adders in Minecraft). At that point you're not really learning anything except how to play Minecraft.
When a student's at middle or high school level I feel like LEGO Mindstorms or even Arduinos would be a better option.