Children have very good bullshit detectors. They know when you try to trick them into learning. They know when something looks like a game but it's actually a chore. Such thing is just not fun. So if you want to go with the path of gaming, make games with side-effect of education instead of education with side-effect of play.
One way you could approach it is by making the skills you want to teach an integral part of the game world, not something that looks like arbitrary limitation. Say, you want to teach kids that moss on trees can be used for navigation, and sun for telling time. Instead of doing stupid quizes about it, just mod Minecraft so that the northen side of tree trunk is green and put some hint in-game that you can use tree's shadow to tell the time. Kids will learn those things as useful in-game skills and transfer them to real-life.
Another example. You know what's the best MO(O)C for basic astrodynamics? Kerbal Space Program. It doesn't try to teach you math and physics, you just need to know some concepts to play effectively, and the more you know, the better you play. And people learn it, and find it fun.