Hi Ferdinant2020,
I'm Nik, an independent advisor here to assist you with this.
It looks like that the "Meet Now" feature is disabled by your IT administrator in Teams meeting policies. Please contact your school IT administrator and make sure that the following
https://docs.microsoft.com/en-us/microsoftteams...
Please refer screenshot from "MS teams admin center" to know the policy details.
Regards
Nik