In all honestly, those fuji-instax cameras are kinda expensive to shoot on a regular basis. I don't know the pricing right now, but 2 years ago it used to cost as much as shooting and developing actual 35mm film (Which has a much higher resolution, even on disposable cameras). The advantage is that you get your photos pretty fast tho, and the retro feel.
I really hope they got monetary support from the school to shoot the portraits.