Hello,

We are an institution, has a Exchange Server (with 80 license)
The question is: as students come and go often, to easy our operation,
 
Do we allowed to create more than 80 user accounts (e.g.150), but only 80 are activated each time, the rest are set to disabled. When students leave, we disable relevant account and activate other account.

or we must buy 150 license?

Thanks for your help in advance

Hi

Welcome to Exchange technet forum, we support for your technical issues, so I recommend you contact Microsoft custome service to consult license or cost question.