I look at some of the responses and face palm at how some people here seem to think they are above the law.
@ the people with the responses of violence only: You're NOT, the only time you are above the law is NEVER. Just because its your property and/or the property you live on doesn't mean you have the right to attack them to
@ OP:
These kids think their tough ****, fine, let them rabble on, all it takes is a phone call, or going out the back way, going to their parents house and showing proof that they are indeed trespassing, then you can sue them all if they don't comply, and you'll get a big wad of cash (before the taxes) in your pocket for it!
Then again, suing over kids being on your porch in some situations can seem pretty stupid, though what they are doing isn't worth potentially getting an assault charge over, which would end with money out of your pocket in which case if you're not very careful.
If these parents do nothing, then it is completely within your rights to sue the hell out of them. If you put a No Trespassing Sign, and they don't stop, you can sue the kids and the parents, charge the kids with civil disobedience, trespassing, as well as harassment, if they have done anything else to you that would be against the law at that point, you can sue them for that too.
You can also sue the parents for not taking proper actions to make their kids stop what they are doing. Which means not only do they get charges against their records, their kids also take the fall. They can get a very high fine if they keep adding up.
Thing is, with the moral decay our country is seeing, doing that will be tough ****.