As has been already said, stripping the finish can be risky.
Another thing to consider is that if you are just going to prepare the existing finish by "roughing it up", I would use very fine sandpaper. Since the existing finish is acrylic urethane, you have to use acrylic urethane to re-spray it. Also, I personally would spray the prepared finish with "primer" for acrylic urethane. This will adhere to the existing finish very strongly and will allow the new coat of acrylic urethane to adhere very strongly to the primer. This should yield a very hard finish that can't be scratched off with a finger nail. You will not want, most likely, to use the wrong paint and have a soft and non-durable finish. Finally you will want to sand the new finish with super fine sandpaper available at auto paint stores that auto body shops buy their paint supplies at. These are like 2000 grit or higher. Work up to the high grit from lower super fine grits and then clear coat it with a clear coat made to go over acrylic urethane paint. Then sand and polish the clear coat without burning it.
Doing this refinish so that it will be super nice looking will be a lot of work, time consuming, and expensive.
It would probably be cheaper to prepare the existing finish and take the guitar, stripped of hardware, etc., to an auto body shop and let them spray it. They already have bulk paint that is super hard and would probably be compatible with the existing finish; meaning that you would not have to strip the entire finish down to bare wood, or spend a "lot" of money on paint and clear coat plus other needed supplies. An auto body shop would probably do it for a very reasonable cost, especially since it is for a school. Just prepping it would be a good learning experience for the students.
To do a really top quality job requires a lot of spray painting expertise and specialized materials and equipment.
Good luck with the project. I'm sure you will try to do your best job.