Hi there this used to be really bad for me when I started teaching in schools and had to sing as well as speak quite loudly over all the kids. The basics you should be doing is warming up yourself at the start of the day, a proper warm up not just what you do with students. A hot drink of lemon and honey through the day if you can manage is good and of course lots of water. Also resting your voice in between as much as possible, no talking or when you are, speaking softly. If you can implement some techniques to try singing less in lessons, maybe make some recordings, singing softly, humming the tune while the student sings it. Take care of your voice, I lost mine once which took quite a few weeks to recover from… sorry it’s happening, so hard to manage sometimes…