you’ll soon realise that upper body strength is less important than you may think, climbing is all about balance and footwork, as you improve you’ll learn to keep your feet below your centre of gravity and your body close to the wall where possible. There’s a couple of decent YouTube channels aimed at beginners / improvers, can’t remember the names tho sorry.
Id recommend going along to your wall this week before the students return,, it’ll be quieter and gives you time to think. Hire comfy shoes and do a little arm stretching to begin with, your forearms will tire quickly if you’ve not climbed before. You’ll see a grading system, usually colour coded, start easy and get better on the same routes, don’t just tick them off and aim for a harder one, there’s fun to be had in polishing your technique and it will pay off.
Enjoy it, I began 15 years ago and still climb weekly, weakly too.