Health: You should call the Hanhalah of the Yeshiva and speak to them about this issue!
If the boys are doing this during yeshiva time and any of them get hurt c”v, it will be the yeshiva which is liable. Believe me, any school which hears the legal term “You will be liable” should take it seriously! And if you speak to them in a way which shows your concern for the safety of the kids rather than angrily or in an accusatory fashion, I think they will understand where you are coming from and take appropriate action.
My son’s yeshiva had the same problem. I spoke to the principal and they took care of it – the kids don’t play in the street anymore.
Also, re: why they would play in the street. You should realize that sometimes kids will do things in groups that they wouldn’t necessarily do individually – sort of like a mob mentality. So it could be that some parents have emphasized to the children that the street is not a place to play, but when “everybody’s doing it”, then that is somehow different to them. Another example of this is when a class gets out of hand with a teacher. Individually, each child may be a good boy/girl and wouldn’t usually be chutzpadik, but when the whole class is making trouble, everyone feels OK to join along.