afinein please check the current docs:
Create Events:
https://support.office.com/en-us/article/get-started-with-microsoft-teams-live-events-d077fec2-a058-483e-9ab5-1494afda578a#bkmk_createliveevents
An Office 365 Enterprise E1, E3, or E5 license or an Office 365 A3 or A5 license.
Attend events:
https://support.office.com/en-us/article/get-started-with-microsoft-teams-live-events-d077fec2-a058-483e-9ab5-1494afda578a#bkmk_attendliveevents
Public Events - No restriction
Private Events - If Teams Live Events just a Teams License and this is included in A1 (for faculty and student)
So you need at least one license to create the live event. From here you are good to go. Public Events are not listed anywhere. It means you just have to know the URL and this one is not guessable. If your students don't have an account (like mine 1-4th grade here in Germany) only A3 accounts are needed for the teachers creating the event. Presenters are good with an A1 license too (as far as I know).