My staff is 6 months and showing agression to small dogs and puppies. Can anyone tell me why this is? He is fine with small dogs when he is with bigger dogs and playing in a group but not on his own. He has been neutered as well. Can anyone help?

Has he been correctly socialised with these types of dogs?  If not, he could have learnt to be agressive to keep them away because he's nervous, or because he is gaurding what he perceives as a valuable resource.....

Has went to puppy classes from the age of 3 months and is at the park all the time with other dogs. Just recently have noticed that its only small dogs. Not sure how to handle the situation, like I said before he is fine with small dogs when he is around other dogs??

Im not an expert but I too have a staff whos now a year old and base anything I know on my experience with him.

The fact that he is ok with small dogs when bigger dogs are around may suggest that he is more confident with the pack order as its clearer to him that the bigger dogs are in charge and he is in the middle and the smaller dogs are at the bottom of the pile! It would mean that when he is with smaller dogs that he is fighting to be top dog (pardon the pun! :) ) When big dogs are around he accepts that he is not top dog.

It may be that he just doesnt like little ones and the bigger dogs are taking the emphasis off which is why he would appear ok when thay are near.

Dogs mature at different rates and show dominance in different ways. I would continue with the classes and continue socailisation. It will probably calm down a little anyway as he matures and he has confidence in himself but whilst I would say keep him on a short leash when little ones are around to avoid them being injured dont avoid them altogether as he will feel that he has something to fear and it will only exagerate the problem.

Just out of interest, What is his behaviour like around little dogs? Do they do anything to provoke? I would say that if a smaller dog runs up yapping at him and he growls back, then thats a totally normal reaction and you would just have to teach him not to overreact. Neutering doesnt always help with these problems either!