Moodle has been around since 2002. its open source and pretty easy to install and maintain. Google classroom, like most other google apps, ablates the responsibility of servers, networking, and an IT staff and in turn allows educational institutions to experience the full wealth of googles Software As A Service. Just imagine, your proctoring a major exam when suddenly your application just disappears in a fashion not unlike the massive gmail outage on 1/24/14. Google has no technical support, no publically available points of contact and zero fucks to give about your students or your lesson plan because you arent the consumer, you're the product.
"Phone support is available for administrators of Google Apps for Business, Education, Government, and Nonprofit accounts." Not sure how that compares to their Google Apps for Business stuff, but that has gone from mediocre to pretty good.
I didn't loose anything in the great outage of 2014, despite having 3 gmail accts and using google docs with it. In fact, I've never lost a google doc in 6-7 years.
And when you hear rants like this, there never seems the possibility that something can disappear in other ways besides a "google outage", or some "cloud cluster fuck". Users never delete things accidentally, or rename them, dogs no longer eat homework, and non-cloud servers never seem to crash, or if they do, there is super-IT man at the ready, and the backups are alway good and easy to pull that one file out that no one can find all of a sudden, and no one ever overwrites a file with an older version, and of course no one would care to backup stuff thats in the google, or other, cloud even though the tech for that exists.