to use two RX during Teacher / Student mode, you have to set one of the RX to "CLONE" mode.
Than you can use the secondary HF-Module to connect to the student TX.
The best way to switch to CLONE and later back to NORMAL mode is to use a physical Jeti-Box.
yes, that's possible using the Jetibox-Emulation inside the Transmitter.
But it is much more complicate, as I know.
Sorry, but I did not have any experience, using the Jeitbox-Emulation, in this case.
All I know is, you connect the second RX to the first RX and than you can access the second RX thru the first one using the Jetibox-Emulator.
It's easy to switch the receiver to clone mode by the transmitter jetibox emulation. But it is not possible to switch back to normal mode by the transmitter directly as the telemetrie of the receiver is deactivated. There you need a physical jetibox.
In the past somebody in this forum showed a way to switch back to normal mode without a physical jetibox but i don't remember how.