And I'm sure you'll give them appropriate temperature gradients. You sound like a great future snake keeper.
You're in a bad situation here, though. You know what is right, but can't do it. I'm going to possibly go against lots of very good animal-care intuitions and suggest that you do exactly what the teacher asked you to do. It is their snake, after all, but more importantly than ownership rights is the fact that you're in a relationship with an severely unbalanced power dynamic.
If harm comes to the snake after (but of course not because) you've made modifications to its care, you'll likely be held responsible. In some relationships, that's a chance that is well worth taking, but I don't think that's the situation here. If the teacher wouldn't listen to reason about the heating situation in the past, I don't imagine that they're the kind of person who will listen to reason after something bad happens. Sorry to have to be so blunt, and I do hope I'm misinterpreting the situation, but in any event you need keep yourself in the clear.
Hopefully the temporary care situation doesn't last so long that any permanent damage is done to the snake from the conditions that its owner stipulated it be kept under. However things turn out, it looks from here like you're doing a great job.![]()