Mic is Live when Entering Meeting

Hello,

Here's our issue.  The host has given mic rights to all participants and they have muted their mics.  A student leaves class (Internet issues, for example). When they rejoin class, their mic is unmuted. And because they had it muted when they left, they may not realize it until the background noise disrupts the class.  

I have looked for a setting to automatically mute mics on entry, but I haven't found one.  Does anyone know where it is?

Thanks