Yerach Ben Yomo, why do you immediately say that these boys are “at risk”, don’t you believe that regular yeshiva boys do this shtik as well? Well YES they do!!!!
Observateen, you did the right thing. Another way to take care of such a situation depending on your age (if you are much older than they are) is to say “Do I know you? I don’t think so. Lets keep it that way”. And move on. They think they are so smart and so cute and dare each other to talk to a girl and get their attention and sometimes they need a “slap in the face” to be put back in their place. A few good embarrassing moments and they will give up.