Lots of good Internet based games: e.g Algebra puzzles which could be used to form the basis for a lesson or also could be used as an intro warm up or early finishers activity. Most activities would suit upper primary, however some extension students would benefit from playing the games.
Has a good selection of logic games e.g. factory balls and popular games, such as battleships.
Has a good selection of instructional maths videos, which look very useful.
Or another one: teachers have repeatedly been found to dislike students who show curiosity and creative thought, even though creativity is held as an important goal of education.
If you’re a student whose teacher constantly thwarts you when you try to do something your own way, you may not have the stamina of M.I.T.’s founders—especially if you come across such resistance at an early age.
Instead, you may find yourself trained to stop your creative thoughts before they are fully formed, lest you get in trouble for voicing something that is “wrong.