For CSA class, your teacher recommends downloading the latest stable build, even though the PLTW curriculum wants you to get an older version. As of 4/3/18, you can get version 3.1.
Installing SDK
The first time you open Android Studio, you need to make sure you have the right SDK (Software Development Kit) installed.
From the opening screen, click the configure button and then select SDK Manager.
You need to install an SDK that will work on your Android device.
As of 4/3/18, our class has access to some devices with Android version 5.1 and others with Android 7.1. If we selected SDK version 22 for Android 5.1, that would work with both of our devices. If you have a personal device that has an older version, install one of the earlier SDK’s to match.
How to check your Android version
When you create your first project, you will have to choose a minimum Android version – remember what version you installed so it matches.
For the examples on this website, I will use SDK version 22 for Android 5.1.*
*Android Studio still makes me install SDK version 26, so ¯\_(ツ)_/¯