Leaving one Team call and then returning without disrupting the first call

Hello Llipton   The scenario you're describing would be perfect for doing a "breakout room."  I've included info here:  https://techcommunity.microsoft.com/t5/microsoft-teams-community-blog/how-to-do-breakout-rooms-in-microsoft-teams-a-real-life-example/ba-p/1506862

You can contact the author of the blog if you need further details.

Here's a video from a Microsoft employee: And a video: https://www.youtube.com/watch?v=d_iD5PLgr08

You don't need to create several call-in numbers for the main class;  if the instruction is to go to the breakout room and then return to the class, they use the same number.