What to do about these kids...?

ok @ my apartment, I live in an upstairs unit, and there are always these kids, who are always playing on the steps. There is one other family who lives upstairs in my right across from me. But anyhow, these kids are so loud and disturbing...they yell, scream, run up and down the steps...They even leave there toys which block the walkway. they do this every single day like all day. Their noise right in front of my door or on the steps also bothers my dog, he starts barking like crazy, which makes my nerves more worse. Last month, the apt man. put a letter on everyone's door saying that you cannot leave your kids unattended, or they may contact CPS. I'm not going to say anything to the kids, because they're kids and I don't want my words to get misconstrued. I'm thinking of notifying the apt man. about the noise and where they play @, and I know it's dangerous for them to play on the steps, and there are no parents watching these kids. What to do??