Here is a list of game engines and tools STEM educators can use to create lesson plans and curriculum for video game based education:
Game Design Tools
This is a master resource list used by Global Game Jam participants. Some of these resources are free and low cost. Most of these are good for middle- high school age and above. I highly recommend Game Maker and or Game Salad game engines since they have a huge community online and there are many tutorials available. You can even publish to the web, and/or test a iPhone or android device.
Basic Game Design Principles
For those on the younger end, Game Star Mechanic is a free website and online ciriculum that teaches game design theory and systems thinking. https://gamestarmechanic.com/
Video Game Ed Curriculum
Their parent company E-Line Media makes educational games and curriculum for educators. Please check them out as well. http://elinemedia.com/
You may also want to join the Institute of Play for teacher support and training using video game curriculum's- http://www.instituteofplay.org/