There's a number of mods around education for it: https://wiki.minetest.net/Mods:Learning
And here's a somewhat elaborate discussion on using it in class: https://forum.minetest.net/viewtopic.php?f=3&t=9482
It also has a really good modding API in Lua, which you could probably get middle school students to have fun with and actually create something in a video game.