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Currently, there is no ETA when instructors will be able to sign up for Schoology Basic accounts. Here's an article that explains Schoology's decision to temporarily disable Basic accounts.
Two years later, no ETA. Education professors won't be able to have their students create accounts to compare LMSs. Additionally, people like me who started with a basic account that was added to our district account will lose those accounts when they leave/retire. FYI, I'll be one of those education professors.