If you (or a student) are typing on a Chromebook and the letters you are typing do not come up as they should, take a quick look down to the bottom right of the screen where the clock is. In the United States what you should see is something that looks like what you see below (notice the US).
The quickest way to "solve" this is to select Ctrl + Spacebar. This should then adjust back to the US keyboard.
If you would like to see more information regarding the keyboard, simply go into the settings, and adjust the different input methods.
In the 1 minute and 3 second video embedded below you will see how to adjust the keyboards.