Configure API Security
Navigate back to https://admin.google.com, and from the Dashboard (admin console), click Security. Click API reference and confirm that the Enable API access box is checked. If it is not checked, check it and click Save on the bottom right.
Click Show more at the bottom of the Security page to reveal Advanced Settings. Click Advanced Settings, then click Manage API client access.
Manage API client access
In this screen, copy the Client ID value that you created in an earlier step and paste it into the Client Name field. Then, copy and paste the following API scopes into the One or More API Scopes section and separate them with a comma. Next, click the Authorize button.
Paste the following into One or More API Scopes.
Classroom Teachers Group
In your Google Admin Console go to Groups, then click the group named Classroom Teachers (firstname.lastname@example.org). Click Manage Users in Classroom Teachers, then add your teachers to this group to enable the Google Classroom feature for your teachers.
Note: Teacher accounts can not be members of a sub-group under the Google Classroom Teachers group. The Teacher accounts must be added directly into the 'classroom_teachers' group