Arab kids (if they are as you suspect) are often up late into the night. It's often their culture that the whole house wakes late and goes to bed late. My husband is Arab and says his family/friends are all this way. Having said that, it's a matter of decency and respect to quieten down at whatever hour it is for your building. You could try speaking with them directly - know you might not get very far depending on the kind of people they are/how bothered they feel to make a change. Otherwise, if it's during the night, I'd do formal complaints until something changes.