AITA for spitting at a backtheif

I was putting down the American flag at my school when as I was folding it some kids stole my bag laying on the ground near the poll. I let it go until I was done when I was done I got the bag thst was left behind a poll and the kids began to laugh and make fun of me for being in a military uniform as I am in JROTC. I spat on ground near them and move into the office. I regret doing so and wish I didn’t but I am not sure if it was wrong for me to do so or if it was justified nor if I’ll get in trouble for doing so. What are y’all thoughts.