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This explains why you wanted x5 cameras :D
What/where do you want to demonstrate?
The 18-55 IS kit lens will struggle in low light/indoors but is cheap and usable outdoors and this model comes with stabalisation.
https://www.mpb.com/en-uk/used-equipment/used-photo-and-video/used-lenses/used-canon-fit-lenses/canon-ef-s-18-55mm-f-4-5-6-is-stm/You could get 2 lenses and pair this with the also very cheap 50mm f/1.8 II that is better in low light and good at demonstrating large aperture lenses / shallow depth of field / portrait style images. The field of view could be a little long for it to be a single lens.
https://www.mpb.com/en-uk/used-equipment/used-photo-and-video/used-lenses/used-canon-fit-lenses/canon-ef-50mm-f-1-8-ii/I started with this combo, the 50mm taught me a lot.
Cheers, sorry should have been clearer - I’m the teacher (it’s not my specialism)! Need to buy some for the students.
Also, ideally I’d like the same lens for all students so I can demo it more easily.