This project can work for a Grade 1 through Grade 6 class depending on how hard the students code the math questions. It is a simple game where one sprite moves at a constant rate, while the other sprite needs to first answer an addition (or subtraction, multiplication and division) question to move forward.
My Grade 3 class will first play this game, then code it for a Grade 1 class and a Grade 6 class. They will have to consider the range of numbers selected in the "operators" blocks of code when doing subtraction, and division.
If they select a smaller number for the first number in the question for subtraction, or division, then their program won't work, not for an Elementary class at any rate.
Here is the video tutorial to get you and your class started:
Here is the project page: