Additional features, settings, or issues not covered by specific Microsoft Teams categories
Susan,
I definitely would NOT recommend your student to use VPN because it is technically against the laws in China to do so.
Using personal account to sign into Teams is no longer possible in China, even if the personal account has a paid subscription. It is not whether it is paid or not that matters. What matters is the account type - if it is personal account, the answer is no.
You certainly can buy them business license so they can continue using Teams, but that's not necessary.
There's one very important detail here - see screenshot below.
You can add the students’ personal accounts to your business tenant as guest users. Once they are added, they can use their guest identities to communicate and collaborate with you within your organization.
A simple way to think about it is this:
Before, you were working inside your office building while each student was working from their own private home. You could still communicate with one another, but everyone remained in their own separate environment.
Adding them as guest users is more like inviting the students into your office building so you can work together inside the same environment.
Before they can enter, you first register their personal identity with your organization. When they arrive, security checks their ID against the information you provided and issues them a guest badge. That guest badge allows them to enter your building and access the areas and resources you have permitted them to use.
In Microsoft 365, their personal account is essentially their ID, while the guest account in your tenant acts like the guest badge that gives them access to your organization.
I think that's probably the best and cost effective way to set up.
Just to make sure, you are using a business license, right? Are you the admin user for the business account?