Coming home to a street where people are constantly coming and going and hanging out outside, is not something that anyone wants. You pride yourself in keeping your street safe and clean and having a group of loitering teenagers outside your home on a regular basis can frustrate even the calmest of people.
The best way to handle the situation is to speak to the loiterers about your concerns. Be bold and go up to the resident that lives there and let them know politely that you would prefer if they found another place to hang out. Don't get discouraged if this does nothing. The point is, you have taken the mature road and spoken like an adult to them fist.
Take matters into your own hands first by speaking to the loiterers, speaking to their parents, speaking to the landlord or property manager, and, if all else fails, you can contact the police.