I agree with both previous posts. Dogs are indeed pack animals and when they do not receive enough human interaction or limitations and allowed what seems like total freedom, they are more apt to develop pack behavior. What breed of dog are they?

One thing I can guarantee is that they are lacking exercise. One common misconception that I see in about 50% of my clients is they think a romp in the yard is adequate exercise. Or being outdoors is adequate. This can be true for a handful of breeds. But what do you think of when you hear the word "exercise?" Exercise is physical exertion - they need good daily walks, jogging, hiking....

Obedience is an excellent idea. However, if you do not provide ground rules, practice daily and prevent them from having free roam, the training will be obsolete. If you have further questions, let me know.