puppy aggressive toward other puppies!

I have a 7.5mth old male Jack Russell Terrier. He is good as gold with adult dogs, and plays nicely with them.

His problem is other puppies, he has never "liked" them, and will go in for the attack whenever he meets one. He is not bighty, but he growls menacingly and tries to pin them down, legs up on shoulders, all the typical dominant behaviours.

Has anyone ever experienced this? My uneducated opinion is that he knows they are pups and can get it over them, whereas he would dare not behave like this toward adults. I can tell within seconds whether a dog is a puppy, which is not always obvious when they are large breeds, but Nugget's attitude gives it away immediately.

I have now gotten to the stage of leashing him as soon as i see another pup, and to try and introduce them slowly, and as soon as he acts up, stop the meeting and walk on.

Does anyone have any insight or advice? Nugget is not my first dog, but my first that has had any negative behaviours.