If I understand correctly that your guitar is left in the instrument room outside of a case...??
as soon as possible it should be in a case, you can lock the latches so no one takes it out and plays it or knocks it around, since it is in a music room, which I didn't understand before than hopefully it is a safe and monitored area...I didn't connect that you are in school I just thought that you often just left it somewhere, which is why I thought that is crazy.
Your guitar will have much less wear and tear by being kept in a case than it would always being out. As far as the climate difference issue from opening it in a room. If the temperature is similar from outside to inside the building I would not worry.
But it is now in winter when you bring a guitar indoors that it is critical that it is left in its case until the case and its contents warm up. Depending how cold outside I would say up to an hour, but at least 15 to 30 minutes..
But it is worse for your guitar to go from outside to inside without being in a case.
The wood and paint will expand and contract from the temperature difference, in a case it will be gradual as it warms up slowly. Ou of a case it is almost instant contraction and/or expansion. The paint cannot elasticize that quickly, thus it will crack and that is why you often see checking on fairly new guitars. in addition the entire guitars stress areas, strings an neck will do the same which is not good for its intonation....

Speaking of music room, ask the other students who are string players how long or what they do to acclimate their instruments. Violins and Violas are quite expensive and much more fragile (as acoustic instruments that are built in the same methods they used centuries ago )
You will never see a violin out of its case unless it is about to be or just has been played .
They always are transported in a case...

BTW....The Gig Bags, don't waste your money, they do not provide enough protection in the event of colliding with anything, Table / desk corners and anything sharp or....
If you take care of your guitar in a case, it will give you back many years of playing...
A lot of Strats and Teles have been shuttled around from gig to gig and have suffered a bit, but in their cases it ensures they are ready to play after arriving at the venue..
More often you will probably ding or dent your guitar when you are playing it rather than any other time.....

Good Luck..