How to record 2 cameras at the same time

I need to record a teacher at the front of a classroom and another session with a camera feed of a whiteboard. Each feed should occupy half of my screen. How can I do this?

I selected the "Gallery View" option and disabled "Record Active Participant." Now I can see the feeds from both cameras on my screen, almost 50% full, but the recording still only shows one of the two feeds.