Photo credit: MathGames
King of Math is a game designed to match the common core standards for math. In spite the fighting aspect of the game, I do like that the skills practiced automatically switch to the next difficulty level seamlessly while playing the game. However, this might be uncomfortable for younger players who may not know the next concept.
Another fun aspect of this game is that winning streaks help you buy upgrades. Mistakes also release a horde of zombies, so keep an eye on younger players to see if this gets too frustrating.
Disclaimer: this game includes the killing of adversaries.