I often deal with Occupational Safety and Health Administration (OSHA)industrial hygiene related issues. Breathing any kind of particulate will eventually harm the lungs.
You first need to have each student "fit tested" for a 1/2-face respirator by a vendor (call Zee Medical Service at 888-225-5933) and they will set you up with their nearest testing and respirator salesperson.
Once each student is fit-tested and has a respirator properly fitted to them, you will need to equip each respirator with P-100 particulate filter cartridges. Ideally you would assign a respirator to each student and they would be responsible for them, including cleaning and maintenance.
Yes this will cost money, but it is worth it to avoid the potential health risk or potential future liability.