anonymous’ story: Harassment in school

Ironically enough last month we had a sexual harassment class. You know when they tell you what is appropriate and what isnt. I thought oh that would never happen in my school. Little did I know that it did. As I was leaving early i see this three kids that were younger than me yet bigger (I am really small) walking up the stairs as I am going down.
I am looking at my phone texting a friend, when this kid calls back “i said hey”. I turn around thinking i might know this person, and i stupidly answered “i dont even know you” he starts getting all worked up saying that i should still say hi and not be rude. That just because im hot and he likes my curves doesnt mean i have to be a stuck up chick.
I just walked away and ignored him, but it bugged me. The whole way down the stairs he kept shouting stuff.
The worst thing is that if i report it the kid will prob just get a detention (if that). Cause my school (a catholic one) does the most retarded punishments, once a kid handcuff some grade 7s to a toilet, punishment: oh a 3 day suspension, no biggie. You steal something, oh no punishment if you give it back, no questions will be asked