There is only one teacher, who carries out tests and administrates students as well. An exchange of questions and tests is possible only within the whole isTest community. An exchange within the group makes no sense, since there is only one teacher in the group.
There is a person responsible for the administration of school classes, students and teachers. Several teachers are possible, who can share questions and tests with the whole isTest community or just only with their colleagues in the group.
Administration of classes, students and teachers is easier in a single license. If nobody is willing to take over the common administration or if the coordination with a common administrator is difficult or laborious, several single licenses might be an alternative to a group license, although they are more expensive. In a single license the licensee is in full control. In a group license it is mandatory that some tasks are performed by an administrator.
After You have created an account You get a free license for 100 days.
60 days before a license expires, You get an invoice for the following 365 days. If You do not extend the license, You get a reminder 30 days before expiration.
If isTest does not suit You or if You do not want to use it any longer, You need not undertake anything. A cancellation is not required. You can just ignore the invoice and the reminder. After expiration of the license isTest is no longer accessible.
In a group license only active teachers are relevant for the license fee. Therefore the administrator can import from a list all the teachers in his organisation without generating additional costs. A teacher becomes active, if he has logged in 10 times. Active teachers are counted for the license fee. If a teacher does not want to use isTest any longer, he must be deleted by the administrator. Later on he can also be imported again, without becoming active again. The login count starts anew.