iPads have a featured titled Guided Access that allows you to lock down the ability to toggle between apps, which allows you to limit students to use only the app the teacher intends them to use.
To Set Up Guided Access
Note: The steps will vary depending on what version of iOS the iPad is running, but the process is still similar across all iOS version. These specific steps are for iOS 13.
1. Go to Settings
2. Click Accessibility
Note: On older versions of iOS, you must select General before seeing the option for Accessibility.
3. Under General in the accessibility menu, select Guided Access
4. Click the radio button to turn on Guided Access
5. Click on Passcode Settings to set a passcode
To Use Guided Access
1. Open the desired app
2. Click the home button 3 times quickly
3. Click Start
To Exit Guided Access
1. Click the home button 3 times quickly
2. Enter the passcode you set previously
3. Click End