If a student gets a prompt that states: "To keep your account safe, Google wants to make sure it's really you" it means they run in to a "Login Challenge" for additional security reasons. Follow the directions below to resolve the issue

1. Go to the Google Admin console

2. Click on Directory…

3. Click on Users

4. Search for the user in question

5. Click on the User Name Link

6. Click on the Drop down in the Security Field

7. Click on the Pencil to the right of Login Challenge

8. Click on the button for Turn Off For 10 Mins

9. Have the user try signing in again