You should make all students as attendees to join the meeting so they don’t have permission to change the setting to the others.
Please Click into Meeting options when you go to the meeting detail from your calendar like the screenshot below.
Then change the setting to “Who can present” to “Only you”.
In this case, we can make all students as attendees by default.
Note: the original idea and screenshot is provide by Lindsey Devillier from Beijing World Youth Academy. Thanks for sharing