Probably not just a scowl. Supes would fly back down to tell them that he is completely disappointed in them for picking on a defensless animal and how they could have hurt a lot of people throwing a scared cat on a busy road. Because imagine just how small you would feel, the utter shrinking shame it must feel like that Superman is disappointed in you that you would just want to crawl into the smallest space you can and not come out because the shame is just that great.
It would make them fess up to their parents, beg to be grounded and change their lives for the better. Superman wouldn't feel great about it either. Making kids feel small. But he knows he can inspire them to be better. To take the right path in life.
Maybe superman will fly by in a few years and see them volunteering in an animal shelter. He might stop in as Clark, doing an article for the planet about how the shelter is helping rehome stray cats, see one or two of those kids grown up, volunteering and smile that he could make a difference at a vital point in their lives and save a life before it has the chance to be lost.
Because that is what Superman does.