Ugly scrote wouldn't stop staring at me even while I was with my mom (who's his TEACHER)

Today I'd gone to a natural dyeing workshop sort of thing with my mom, who teaches at a super well-known and top-ranked fashion college in my country. From the moment I saw this ugly scrote, I knew he was a LVM perv weirdo.

He would constantly stare at me even while I was turning around to look at other things than his bearded ass scrote face, and mind you this dude is probably 22-24 ogling at a girl way younger than him, while his literal teacher (my mom) was right next to me the whole time. I'm not even 20 yet and I look so much younger than my real age because I'm short, to imagine a GROWN MAN staring at someone who looks undoubtedly too young for him is so fucking repulsive. No wonder this scrote made me so uncomfortable the entire time I was there.

In the end, he kept looking in my direction for no reason so I purposefully went and stood behind a woman so he'd finally stop ogling. And I'd have to stop looking at certain things around me that seemed interesting just so he'd finally be out of my sight. He then had the audacity to come sit with me and my mom along with this other female student, who he was talking to so condescendingly.

The whole time I just kept thinking "why the hell do males act like uncivil dogs who can't keep their stares to themselves when they see a young girl?"

I make faces at random ugly older men who stare at me but I couldn't do anything this time because everyone in this workshop knew my mom and I didn't want to come across as "rude" or "aggressive" in case someone saw me making a face.

Does anyone know of ways to get scrotes (random and acquaintance scrotes, both) to stop staring? Should I have stared at him angrily instead? Or maybe I should've given him a prolonged blank face stare since I look intimidating when I do that.