Hi @RobB
Yes, based on our research, there is no direct way to convert an existing team to a class in Microsoft Teams. You have to create a new team and set it as a class at the start.
Meanwhile, to get this feature more quickly, we recommend you give the feedback in Teams UserVoice. Many features of our current products are designed and upgraded based on customers’ feedback. With requirements like this increase, the problem may well be released in the future. Thanks for your understanding and support.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.