History
Google Classroom was announced on May 6, 2014, with a preview available for some members of Google's G Suite for Education program. It was released publicly on August 12, 2014.
On June 29, 2015, Google announced a Classroom API and a share button for websites, allowing school administrators and developers to further engage with Google Classroom. On August 24, Google integrated Google Calendar into Classroom for assignment due dates, field trips and class speakers.
In March 2017, Google opened Classroom to allow any personal Google users to join classes without the requirement of having a G Suite for
Education account, and in April, it became possible for any personal Google user to create and teach a class.