This Google Slides presentation gives a thorough explanation of key signatures: what they are, what they do, how to read them, and how to find the major keys they represent; as well as the Orders of Flats/Sharps and the Circle of Fifths/Fourths. It also includes a lesson script in the Speaker Notes embedded in the Slides file (you can view these in editing mode by going to Insert >> Show Speaker Notes; or in presenting mode by hovering your mouse near the bottom of the screen until the Toolbar shows up and selecting Notes).

I've used this presentation and lesson with my beginning band students as well as my high school musicians; it can easily be used for all secondary school ages in performing or non-performing music classes as new content or a refresher. I've personally used it for Distance Learning purposes and found great success, though it just as easily be used in the physical classroom. The animations of objects serve to enhance the learning experience while providing visual interest.

There are also many examples of questions to ask students and slides dedicated to having students determine how to find major keys based on the key signature. (Note: I use the "second to last flat" and "step above the last sharp" methods of finding major key names.)

I hope you find this useful! Please send me a message if you have any questions, concerns, or suggestions for the product.