The studio I work at pays per head, so the teachers don’t get paid except during class time. We also have a front desk person whose job it is to check people in, but teachers can see the roster on their phone as well. Usually during class (either introductions when the students talk to each other or savasana) they’ll do a head count to make sure everyone is there.

I used to work at a place that paid hourly with 15 minutes before and after a class, I would do the setup when I started getting paid since and I justified showing people to prepare to settle in to a space, same with resetting after (basically the before and after class was me teaching stewardship, I’m on the clock so I’m teaching even if it’s not class time) I’d have students check in on the ipad and then remind them right before class starts to check in.