Women, girls, females in general, a popular alternative for weapons for self defense is the below, mace.   I have lived homeless in Dc for almost 13 years, knives are very popular here amongst the homeless population, esp amongst blacks, who have pulled them out in public, in homeless shelters sometimes, and there have been several murders.  A black woman wanted to give me a knife for self protection, like 10 years ago, i said no.  

If a person is more interested in self defense, than harm, pepper spray, mace, etc, is a popular, good alternative to a knife, and oddly enough to many, guns in homes, during a home invasion, the intruder often uses the owner's weapon(s) against the owner(s), people living in the home.

If he was afraid of violence towards himself, he should have bought something like the below.

Bringing mace, pepper spray, or similar defense sprays onto K-12 school property is generally prohibited nationwide. Even in states where carrying self-defense sprays is legal, local school districts usually enforce strict zero-tolerance policies. Unauthorized possession can lead to suspension, expulsion, or police notification. [1, 2, 3]

Rules regarding self-defense sprays on school grounds vary depending on the specific location and the age of the individual: