Plug the student’s instrument through the first channel of your audio interface.
Plug your own instrument through the second channel of the audio interface.
Run the sound/tones through any amp emulation software and output it through your device's speakers. You can tell Yousician to only recognize any of the channels of your interface (change input device). This means you can play along with your student, so you are both rocking out, but Yousician will ONLY recognize the student’s playing, and you are not hindering their score.