I am in Washington State, and I don't know if other states have such provisions in their laws. My 18 year old daughter carries pepper spray, including to high school (she is a senior due to her birthday). One of her teachers told her she couldn't carry pepper spray at school. The teacher was wrong, and I provided my daughter with the citation that the teacher was wrong.
https://www.k12.wa.us/safetycenter/Weapons/default.aspx
Protective Spray Devices
Under RCW 9.91.160, students age 14 years and older may legally possess personal protective spray devices (such as Mace and pepper spray) if that student has parent permission. Schools or other units of government may not prohibit the possession of personal protection spray devices, if the student is at least 14 years of age with parent permission, or of any person age 18 or older.
If your teenager doesn't have pepper spray or Mace at school..... why not?
https://www.k12.wa.us/safetycenter/Weapons/default.aspx
Protective Spray Devices
Under RCW 9.91.160, students age 14 years and older may legally possess personal protective spray devices (such as Mace and pepper spray) if that student has parent permission. Schools or other units of government may not prohibit the possession of personal protection spray devices, if the student is at least 14 years of age with parent permission, or of any person age 18 or older.
If your teenager doesn't have pepper spray or Mace at school..... why not?