Most WordPress booking plugins are built around appointments: one client, one time slot. A class business sells something different. Each class has a capacity, regulars buy packs and memberships, and a full class needs a waitlist that fills itself.
Junocal Booking shows your Junocal booking page on your WordPress site, and Junocal runs the timetable, credits, renewals, reminders and payments behind it. Bookings and card payments aren't stored in your WordPress database, so there's nothing extra to back up or secure.
It suits solo instructors and studios alike, from one yoga teacher with a weekly class to a pilates studio with several rooms. Plans start at $15 a month, month-to-month, with no annual contract.