Access History
You can check the access history of each account by logging in to the Web Admin Page with the Admin account.
To check the access history, please select "Teachers" or "Students", then select "Access History" from the "▼" on the right side of the account.
https://gyazo.com/436f97a5b3c6a58dafe6255ee619c1be
Reference
Check that you are not using a password that anyone can guess