As the host or co-host in a meeting, you can manage your participants, including muting and unmuting participants to manage background noise and distractions. All participants can also mute or unmute themselves, unless the host has prevented them from unmuting.
Due to privacy and security reasons, the host cannot unmute other participants without their consent. The host can either use the Ask All to Unmute option, which will prompt every user to unmute themselves, or can schedule the meeting with Request permission to unmute participants enabled, which will prompt the participants for pre-approval to be unmuted by the host.
When you schedule a meeting, under meeting options, enable the option "Request permission to unmute participants"
Once the students Sign In and join your meeting, they will be prompted to allow you to unmute them when they join any meetings you started.
If a student provides consent to be unmuted, you will have the option to unmute each person individually as needed from the participants list.
Once consent has been given to a host, any future meetings with this host and this setting enabled will have the same pre-approved consent.
Meetings without this setting will require the host to ask each student to unmute themselves.
If the students did not provide consent, you will see the regular Ask to Unmute / Mute options in the participants list.
Guide: https://support.zoom.us/hc/en-us/articles/203435537-Muting-and-unmuting-participants-in-a-meeting