It's not that easy to hurt somebody enough to make a real difference without weapons. Getting angry and taking ineffective action is one more thing that people will mock you for and further contribute to your worthlessness just as much as the principal telling you that you have no recourse for what is happening to you.

My acting teacher told me about her fantasy of punching somebody in the face and I told her that when I tried that as a kid and really hurt my hand. In fact there was a time my son got mad and hit me in the arm and I didn't find it especially painful but his hand was still hurting 10 hours later. Usually your hand is less durable than whatever it hits, particularly the rather large bones in the face, it is a big subject of martial arts to mitigate that. Someone who smacks you has to balance the intimidation power of the smack vs the very real sting they'll experience. Packing a roll of dimes in your pocket is a deniable way (like the clipboard carried by a store manager confronting shoplifters) that can greatly improve the pain factor for both your target and yourself.