I went in today and found both rats still in the tank with no signs of the snake. I cleaned their tank (rodents are fairly gross) and got them new food and water. After school I moved them to my classroom, keeping the lid on this time. I noticed that one of them died at some point today

They had constant food and water with places to burrow and hide. Not really sure what happened, but the other one is still in the tank.

I also laid down a UTH with a thermostat and a hide with water nearby. I will be honest, I am losing hope...but I will continue this all year if needed.